2018-02 Db2 Catalog Statistics revisited

Db2 Optimizer & access path selection for Db2 11 & Db2 12 :

Db2 Catalog dataProblematic default values | Correlations in the Db2 Catalog 

It has been six years since the last update so I thought, after Terry Purcell’s excellent presentation in January 2018, it would be a good point in time to go over and rake the coals again—especially as a couple of things have changed for Db2 12!


Terry Purcell – Db2 12 for z/OS Optimizer and RUNSTATS improvements
Webcast replay          Abstract

Are you a RUNSTATS Master?

Every now and again, I hold a little presentation called “Are you a RUNSTATS Master?” Actually these days it’s called “Db2 z/OS Lies, Damn Lies, and Statistics…” where I describe in detail, what the Db2 Optimizer uses for access path selection in relation to the Db2 Catalog data.

Surprised? You will be!

Personally, I am always surprised at how often people say “just that data?” or “is that it?” (the various other reasons for access path selection like CP speed, RID Pool size, Sort Pool size, Max data caching size, and, of course, the 80 bufferpools are also mentioned, but these have nothing to do with RUNSTATS).

So generally the answer is “Yes.” However, the permutations and combinations make the devil in the detail – The Db2 Optimizer’s algorithms are top secret, but the input data it uses is fully described in the documentation.

Just the facts ma’am

What I want to do, is show :

  • the Db2 Catalog data that is used
  • the default values that can cause surprising things to happen
  • the problem of correlations in the Db2 Catalog

Which data are used by the Db2 Optimizer and which are updated by RUNSTATS?

Here is a complete list of the eleven tables used by the Db2 Optimizer:

  1. SYSIBM.SYSCOLDIST
  2. SYSIBM.SYSCOLSTATS *
  3. SYSIBM.SYSCOLUMNS
  4. SYSIBM.SYSINDEXES
  5. SYSIBM.SYSINDEXPART
  6. SYSIBM.SYSKEYTARGETS (same as SYSCOLUMNS)
  7. SYSIBM.SYSKEYTGTDIST (same as SYSCOLDIST)
  8. SYSIBM.SYSROUTINES
  9. SYSIBM.SYSTABLES
  10. SYSIBM.SYSTABLESPACE
  11. SYSIBM.SYSTABSTATS

* degree of parallelism only and, after APAR PK62804, also „sometimes“ used to bound filter factor estimates…

By the Columns

Now we can also list out all of the columns (obviously not including the key columns) which are used by the Db2 Optimizer:


SYSCOLDIST
CARDF, COLGROUPCOLNO, COLVALUE, FREQUENCYF, HIGHVALUE, LOWVALUE, NUMCOLUMNS, QUANTILENO, STATSTIME


SYSCOLSTATS
COLCARD, HIGHKEY, LOWKEY


SYSCOLUMNS
COLCARDF, HIGH2KEY, LOW2KEY


SYSINDEXES
CLUSTERING*, CLUSTERRATIO, CLUSTERRATIOF, DATAREPEATFACTORF, FIRSTKEYCARDF, FULLKEYCARDF, NLEAF, NLEVELS


SYSINDEXPART
LIMITKEY*


SYSKEYTARGETS
CARDF, HIGH2KEY, LOW2KEY, STATS_FORMAT


SYSKEYTGTDIST
CARDF, KEYGROUPKEYNO, KEYVALUE, FREQUENCYF, HIGHVALUE, LOWVALUE, NUMKEYS, QUANTILENO, STATSTIME


SYSROUTINES
CARDINALITY*, INITIAL_INSTS*, INITIAL_IOS*, INSTS_PER_INVOC*, IOS_PER_INVOC*


SYSTABLES
CARDF, EDPROC*, NPAGES, NPAGESF, PCTROWCOMP


SYSTABLESPACE
NACTIVE, NACTIVEF


SYSTABSTATS
CARD, CARDF, NPAGES


Notes: * Columns are not updated by RUNSTATS and _ Columns are not updatable at all. The column STATSTIME is used only if there are duplicates in the SYSCOLDIST table, and then the Db2 Optimizer will use the “newer” data that was probably inserted by a User.

Know your defaults

Which default column values trigger the Db2 Optimizer to use its own internal default values?


SYSCOLUMNS


If COLCARDF                       = -1 then use 25


SYSINDEXES


If CLUSTERRATIOF            = 0 then use CLUSTERRATIO


If CLUSTERRATIO              = 0 then use 0.95 if the index is CLUSTERing = ‘Y’ otherwise 0.00


DATAREPEATFACTORF    = -1 then is ignored


If FIRSTKEYCARDF            = -1 then use 25


If FULLKEYCARDF             = -1 then use 25


If NLEAF                              = -1 then use 33 (Which is SYSTABLES.CARDF / 300)


If NLEVELS                         = -1 then use 2


SYSROUTINES


If CARDINALITY                  = -1 then use 10,000  


If INITIAL_INSTS                 = -1 then use 40,000


If INITIAL_IOS                     = -1 then use 0


If INSTS_PER_INVOC        = -1 then use 4,000


If IOS_PER_INVOC            = -1 then use 0


If IOS_PER_INVOC            = -1 then use 0


SYSTABLES


If CARDF                             = -1 then use 10,000


If NPAGESF                      <= 0 then use NPAGES


If NPAGES                          = -1 then use 501 (Which is CEILING (1 + SYSTABLES.CARDF / 20))

Here you must be very careful if using NPGTHRSH ZPARM as 501 is more than the default value in most shops. This is one of the little changes in Db2 12 where the value -1 is treated as -1 for the NPGTHRSH check.


SYSTABLESPACE


If NACTIVEF                     = 0 then use NACTIVE


If NACTIVE                       = 0 then use 501 (Which is CEILING (1 + SYSTABLES.CARDF / 20))


SYSTABSTATS


If CARDF                         = -1 then use 10,000


If NPAGES                       = -1 then use 501 (Which is CEILING (1 + SYSTABSTATS.CARDF / 20))


So now you can see that non-floating point “old” data, may still be used today and this may cause access path headaches!

Never ever say never

Now to top it all, the data in the SYSCOLDIST and SYSKEYTGTDIST never gets simply “deleted”.

Well, actually, in Db2 12 you can now do a RUNSTATS xxx.yyy RESET ACCESSPATH to delete all SYSCOLDIST and SYSKEYTGTDIST data and set all other relevant columns to their respective defaults, but you must time this RUNSTATS very wisely! If you run it and then forget to do a normal full RUNSTATS…

Oldie but a goldie

Once the data are inserted, they stay there, until they are overwritten by new data, a RUNSTATS RESET, or the object is dropped. This all leads to some very old data in these two tables that can and do cause the Db2 Optimizer a ton of grief! One of the first things I do is to simply select the MIN(STATSTIME) from these tables just to see how old the data really is. Do it yourself and be surprised! I have seen sites with eight-year old data in the SYSCOLDIST and that cannot be good!

Correlate the world

Now onto correlations… There are lots of little tricks that DBAs use to “massage” access path choice. One of these, is to just set NLEVELS to 15 for a given index. Then lots of queries simply refuse to touch it as it would appear to be HUGE. Now, just simply updating columns can cause the Db2 Optimizer, in the best case, to ignore the updates or, perhaps, makes things even worse! So here is a list of the correlations (In other words, if you change xxx remember to change yyy and zzz as well):

Relationships exist among certain columns of certain tables:

  •       Columns within SYSCOLUMNS
  •       Columns in the tables SYSCOLUMNS and SYSINDEXES
  •       Columns in the tables SYSCOLUMNS and SYSCOLDIST
  •       Columns in the tables SYSCOLUMNS, SYSCOLDIST, and SYSINDEXES

 If you plan to update some values, keep in mind the following correlations:

  •  COLCARDF and FIRSTKEYCARDF/FULLKEYCARDF (They must be equal for the 1st column and full, if a single column index)
  •  COLCARDF, LOW2KEY and HIGH2KEY. (For non-default COLCARDF LOW2KEY and HIGH2KEY key must be filled with data) and if the COLCARDF is 1 or 2 Db2 uses LOW2KEY and HIGH2KEY as domain statistics to generate frequencies.
  • CARDF in SYSCOLDIST.  CARDF is related to COLCARDF and FIRSTKEYCARDF and FULLKEYCARDF. It must be at a minimum
  • A value between FIRSTKEYCARDF and FULLKEYCARDF if the index contains the same set of columns
  • A value between MAX(colcardf of each col) and the product of all the columns COLCARDFs in the group
  • CARDF in SYSTABLES. CARDF must be equal or larger than any other cardinalities, such as COLCARDF, FIRSTKEYCARDF, FULLKEYCARDF, and CARDF in SYSCOLDIST
  • FREQUENCYF and COLCARDF or CARDF. The number of frequencies collected must be less than or equal to COLCARDF for the column or CARDF for the column group
  • FREQUENCYF. The sum of frequencies collected for a column or column group must be less than or equal to 1

New in Db2 11

In Db2 11, the table SYSSTATFEEDBACK was introduced giving us the first chance to see what the optimizer thinks is missing. This is truly awesome, as then we can tailor our RUNSTATS to generate exactly what the optimizer needs to really validate and generate a good, stable access path. Of course, you should be a little bit careful with this data as too much of a good thing can be bad for you!

New in Db2 12

(Not just the lowercase b!)

In Db2 12, the SYSSTATFEEDBACK was made even more interesting by now externalizing the required RUNSTATS options *directly* into the already existing RUNSTATS profile or, indeed, actually creating a RUNSTATS profile for you.

I think that is really dangerous, as then you could easily flood your system with bogus stats for end user QMF/SPUFI queries that were run “by accident,” or so called “boss queries” where someone with *no* idea of SQL clicks together a highly complex and badly written SQL before letting it run for a weekend. Naturally the SQL gets rewritten by a helpful ever present DBA, but the statistics recommendations have now landed in the profile and will be updated and kept from this point on.

My personal recommendation is to switch off this feature as it is sadly *on* by default!

Here are the ZPARMs of interest

ZPARM STATFDBK_SCOPE set to ALL by default.
ZPARM STATFDBK_PROFILE set to YES by default.
Plus, in table SYSIBM.SYSTABLES column STATS_FEEDBACK is set to Y by default.

Out-of-the box it starts automatically creating (for TYPE=’C’ with NUMCOLS > 1 and TYPE=’F’ or ‘H‘) profiles and updating existing profiles…Here you must manually check the size of your profiles every now and again just to make sure everything is ok!

One other new thing in Db2 12, is that XML columns can get statistics now to help XMLEXISTS get a better access path.

and finally

Do not forget that our little Freeware tool StatisticsHealthCheck will find all bad correlations, old data and badly updated data for you and it is FREE!

So I hope this little round-up of Db2 Catalog Statistics data was interesting, and, as usual, if you have any comments or questions, then please, feel free to mail me!

TTFN

Roy Boxwell

 

 

Southwest Db2 Users Group – February 2018

Db2 Forum.  Southwest Db2 Users Group – February 2018 – Grapevine (Dallas), TX, USA

SEGUS & SOFTWARE ENGINEERING proudly sponsor this event & present

1 – Pdf Präsentation Compliance with compliments! Viable Db2 z/OS workload tracking.

2 – Pdf Präsentation Db2 12 Continuous Delivery – New challenges for deployment.

3 – Pdf Präsentation –  Db2 z/OS Lies, Damn Lies, and Statistics… 


1 – Db2 z/OS Security Audit: Compliance with compliments! Viable Db2 z/OS workload tracking.

Audit and Compliance is a need that many companies want and have to fulfill.

There’s different ways and tools that promise to be able to do it, but what can they really do and what are the associated costs? This presentation introduces Db2 10/11 technology exploitation that delivers any DML, DDL, DCL being executed in a Db2 environment along with identification details. Learn how you can run Audit analytics against a long‐term repository, pinpointing who executed a query, when and from where. Analyze your entire workload to understand access patterns and abnormalities.


More about Db2 Audit

Presentation Outline

  • Audit needs and musts Take a journey to GLB HIPAA PCI‐DSS Basel III Sarbanes‐Oxley CA SB1386 Federal Information Security Management Act “ed Flag”Rules (FRCA)5.
  • Solution overview and their Pros/Cons Get an overview about the existing solutions and understand how they work.
  • The viable way – let Db2 do the magic! Learn about Db2 enhancements in Db2 10/11 that deliver the Db2 workload being processed and understand why it’s so efficient.
  • Customer results from the banking industry Receive some experience from a large banking company and how they successfully replaced their Db2 Audit feature based reporting by a modern SQL tracking and analytics process.

 


2 Db2 12 Continuous Delivery – New challenges for deployment.

Fundamental changes in the Db2 z world often lead to concerns. Let’s face it – some changes force us to change! While a Db2 version migration usually took months, or even years, there will be no new Db2 version after 12, but continuous code drops.

This will have a tremendous impact on migration strategies, because we have to find a reliable way to test these code deliveries in a fraction of time. If we make it, Business Divisions will become enthused at how quickly new technology becomes available for new applications. This presentation will describe the difference between Code, Catalog, Function and Application Levels, how you can control them and how you can fallback in case of anomalies. It also illustrates how we still can be pro-active in testing without burning weeks and months.
Learn how to choose from four different levels of testing and a new way of automation. CD-Screening allows you to pick and choose from KPI based test automation. The levels include simple anomaly alerting, access path verification, clone Pre-apply and even workload capture/replay to easily discover different behaviour resulting from a new code Level.


More about Db2 Continuous Delivery – CD

Presentation Outline

Joining this presentation, you’ll learn how to align Continuous Delivery to your Continuous Availability.

  • Agile, Continuous Delivery, DevOps – just buzz words, or new methodologies?
  • Db2 Code, Catalog, Function and Application Levels – differences and dependencies.
  • Activation/Deactivation of new code and how to fallback and when you can’t.
  • Different flavors of (pro-active) CD-Screening and how it can be automated:

* Anomaly alerting based on Incompatibility Change Indicators (ICIs)
* Dyn./Stat.Access Path Change Detection e.g.via Plan Management
* Clone based code change pre-apply exploiting Backup System
* Workload-KPI verification using SQL replay and KPI comparison

Audience Experience:   Intermediate Advanced
Platform:                        Db2 z/OS
Presentation Length:     60 minutes
Presentation Category:  Database Administration Performance Management Db2 Migration

 


3 Db2 z/OS Lies, Damn Lies, and Statistics…

– Benjamin Disraeli, Prime Minister of England (1868, 1874-1880)

The above line may, or may not, have been spoken well over 100 years ago, but the need for statistics and, above all else, accurate statistics is more important than ever in the Db2 world of today.


More about Db2 RUNSTATS

Presentation Outline

  • Db2 RUNSTATS basics & catalog tables and Columns used for access path
  • IBM recommendations through the ages : from Db2 V3 to Db2 12
  • Db2 RUNSTATS advanced
  • SYSCOLDIST explained
  • RUNSTATS real world Q&A :
    use of SAMPLE, COLGROUP, PROFILE, REOPT (ONCE), TABLESAMPLE SYSTEM, HISTOGRAM, …
  • RUNSTATS reversal

Speaker biography

Roy Boxwell has more than 32 years of experience in MVS, OS/390, and z/OS environments – 30 of those in Db2. He specializes in installation, migration, and performance monitoring and tuning. Roy leads the SEG development team responsible for the real time database maintenance solutions. He is also an active participant, speaker and contributor on the IDUG Db2 Listserv and sends out a monthly Db2 z/OS Newsletter.

Heart of Texas Db2 Users Group – February 2018

HOTDUG – Heart of Texas Db2 User Group – February 2018 –  Austin, TX, USA

SEGUS & SOFTWARE ENGINEERING proudly sponsor this event & present

1 – Pdf PresentationCompliance with compliments! Viable Db2 z/OS workload tracking.

2 Pdf PresentationDb2 12 Continuous Delivery – New challenges for deployment.

3 Pdf PresentationDb2 z/OS Lies, Damn lies, and Statistics… 


1 – Db2 z/OS Security Audit: Compliance with compliments! Viable Db2 z/OS workload tracking.

Audit and Compliance is a need that many companies want and have to fulfill.

There’s different ways and tools that promise to be able to do it, but what can they really do and what are the associated costs? This presentation introduces Db2 10/11 technology exploitation that delivers any DML, DDL, DCL being executed in a Db2 environment along with identification details. Learn how you can run Audit analytics against a long‐term repository, pinpointing who executed a query, when and from where. Analyze your entire workload to understand access patterns and abnormalities.


More about Db2 Audit

Presentation Outline

  • Audit needs and musts Take a journey to GLB HIPAA PCI‐DSS Basel III Sarbanes‐Oxley CA SB1386 Federal Information Security Management Act “ed Flag”Rules (FRCA)5.
  • Solution overview and their Pros/Cons Get an overview about the existing solutions and understand how they work.
  • The viable way – let Db2 do the magic! Learn about Db2 enhancements in Db2 10/11 that deliver the Db2 workload being processed and understand why it’s so efficient.
  • Customer results from the banking industry Receive some experience from a large banking company and how they successfully replaced their Db2 Audit feature based reporting by a modern SQL tracking and analytics process.

 


2Db2 12 Continuous Delivery – New challenges for deployment.

Fundamental changes in the Db2 z world often lead to concerns. Let’s face it – some changes force us to change! While a Db2 version migration usually took months, or even years, there will be no new Db2 version after 12, but continuous code drops.

This will have a tremendous impact on migration strategies, because we have to find a reliable way to test these code deliveries in a fraction of time. If we make it, Business Divisions will become enthused at how quickly new technology becomes available for new applications. This presentation will describe the difference between Code, Catalog, Function and Application Levels, how you can control them and how you can fallback in case of anomalies. It also illustrates how we still can be pro-active in testing without burning weeks and months.
Learn how to choose from four different levels of testing and a new way of automation. CD-Screening allows you to pick and choose from KPI based test automation. The levels include simple anomaly alerting, access path verification, clone Pre-apply and even workload capture/replay to easily discover different behaviour resulting from a new code Level.


More about Db2 Continuous Delivery – CD

Presentation Outline

Joining this presentation, you’ll learn how to align Continuous Delivery to your Continuous Availability.

  • Agile, Continuous Delivery, DevOps – just buzz words, or new methodologies?
  • Db2 Code, Catalog, Function and Application Levels – differences and dependencies.
  • Activation/Deactivation of new code and how to fallback and when you can’t.
  • Different flavors of (pro-active) CD-Screening and how it can be automated:

* Anomaly alerting based on Incompatibility Change Indicators (ICIs)
* Dyn./Stat.Access Path Change Detection e.g.via Plan Management
* Clone based code change pre-apply exploiting Backup System
* Workload-KPI verification using SQL replay and KPI comparison

Audience Experience:   Intermediate Advanced
Platform:                        Db2 z/OS
Presentation Length:     60 minutes
Presentation Category:  Database Administration Performance Management Db2 Migration

 


3Db2 z/OS Lies, Damn lies, and Statistics…

– Benjamin Disraeli, Prime Minister of England (1868, 1874-1880)

The above line may, or may not, have been spoken well over 100 years ago, but the need for statistics and, above all else, accurate statistics is more important than ever in the Db2 world of today.


More about Db2 RUNSTATS

Presentation Outline

  • Db2 RUNSTATS basics & catalog tables and Columns used for access path
  • IBM recommendations through the ages : from Db2 V3 to Db2 12
  • Db2 RUNSTATS advanced
  • SYSCOLDIST explained
  • RUNSTATS real world Q&A :
    use of SAMPLE, COLGROUP, PROFILE, REOPT (ONCE), TABLESAMPLE SYSTEM, HISTOGRAM, …
  • RUNSTATS reversal

Speaker biography

Roy Boxwell has more than 32 years of experience in MVS, OS/390, and z/OS environments – 30 of those in Db2. He specializes in installation, migration, and performance monitoring and tuning. Roy leads the SEG development team responsible for the real time database maintenance solutions. He is also an active participant, speaker and contributor on the IDUG Db2 Listserv and sends out a monthly Db2 z/OS Newsletter.

2017-11 Db2 APAR list: An APAR a day keeps the bugs at bay

Db2 12 APAR – time saving list

With all the talk about “agile” going on, and referring to one of my older 2017-09 newsletters* on APARS, I think it is time to tell you all about another little service that our company offers.

(completely free, simple and no marketing spam)


Db2 12 Agile & APAR previous newsletter:

2017-09: Db2 12 SQL Access path: Death by APAR :  How many APARs really can affect access paths?

APAR Database

The APAR database can be accessed by anyone with an IBM Userid and you can merrily search to see if the problem that you have hit is already found and fixed, or a fix is in the works.

The problem is: What about the bugs that you do not *know* you have hit?

Get someone else to do the donkey work

The answer is to get someone else to do all the research for you, and deliver the answer by e-mail every month for all current releases of Db2 going back two years.

Who is that donkey? You will never guess…  😉

Three is the key

There are three Excel spread sheets here.


  1. SQL Performance
    The first is RTS. This lists any and all APARs to do with the Real-Time Statistics tables. If you rely on these tables to decide when to run REORG, COPY and RUNSTATS, then you want to make sure that they are being correctly updated, don’t you?


  2. SQL Access Path
    The second is RUNSTATS. RUNSTATS is a critical utility program and contains bugs like any other non-trivial program. I count RUNSTATS bugs as *always* a personal HIPER. I rely on statistics and so does the Db2 Optimizer. If there is bad data here, then your access paths have no chance!


  3. Performance PTFs
    Finally, and the biggest list, is those APARs that have anything to do with SQL Performance and SQL Access paths (If not already in the RUNSTATS list of course!) Performance PTFs are pretty important!

Going hyper over HIPER

All the APARs have their related PTF. A handy little HIPER column tells you whether or not this is a really important fix. As I mentioned, I treat the RUNSTATS ones as personal HIPERS. Also added is a PE indicator when a PTF goes bad on you (PTF in Error) so you can see if you introduced a problem by correcting another.

One Excel Example: The SQL Performance spread sheet

Db2 12 APAR list free for Db2 z/OS: SQL Performance (RTS) - Performance PTFs - SQL Access Path (RUNSTATS) -

This is from the SQL Performance spread sheet and you can see how it looks

The same table in HTML:

APAR CLOSED STATUS Db2 10  Db2 11 Db2 12 HYPER Description
PI85305
2017-11-01
Closed
N/A
UI51606
UI51601
INEFFICIENT INDEX CHOSEN WHEN INDEX CAN DO INDEX SKIPPING…
 PI85418
 2017-19-25
Modified
UI50098
UI50099
UI50582
PREPARE TAKES LONG TIME AND HIGH CPU IF THE QUERY CONTAINS MA…
 PI85463
New & Closed
 N/A
 N/A
UI51342
TABLESPACE SCAN INSTEAD OF INDEX ACCESS – WITH INDEX HAVIN…

 …

 …

 …

 …

 …

 …

 …

 …

Interested in making your life a little bit easier and safer?

If you are interested in Db2 APARs and you have *no* time to go and scrabble around the internet trying to find out which APARs are needed, worthwhile, or dangerous, then

just email our technical support techsupport@seg.de and ask to be added to the APAR Mailing list.

It is completely free, you will not get marketing spam and it really is as simple as that!

 

Get AGILE now!

With these handy lists, you can quickly and easily review the state of your Db2, and react quickly and in a timely manner when you have to.

 

As usual, if you have any comments or queries please feel free to drop me a line!

TTFN

 

Roy Boxwell

2017-09 Db2 12 SQL Access path: Death by APAR

We recently held one of our Design Councils, this one was all about Db2 12 and going Agile. I was asked the following question after one of my presentations about verifying Db2 Code/Catalog/Function Levels:

“How many APARs really can affect access paths?”

I had to admit that I did not know the answer – I *hate* not knowing things, so I set off to find out how many Db2 Optimizer-relevant APARs there were in 2016 up until today (Oct 17th 2017).

 

Db2 12 APAR review sqlaccesspath

First I used this search argument, as I am only interested in Db2, sqlaccesspath keyword related APARs, those that have an Optimizer relevant CSECT, are HIPER and in Db2 12:

5740xyr00 AND sqlaccesspath AND dsnxo* AND yesHIPER AND C10

1.     PI69349: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query       2017-04-14

 

Remove the yesHIPER and you get 22:


1.     PI82797: LESS FILTERING INDEX SELECTED FOR INNER TABLE OF NESTED LOOP JOIN
A smaller, less filtering index is selected for the inner table with a Nested Loop Join.      2017-10-02

2.     PI78122: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-10-02

3.     PI83289: QUERY ACCESS PATH MAY BE UNPREDICTABLE FOR A QUERY WHERE THERE ARE EQUAL PREDICATES COVERING ALL THE COLUMNS ...
Query access path may be unpredictable for a query where there are equal predicates covering all the columns of a unique index.        2017-09-02

4.     PI83454: INEFFICIENT ACCESS PATH IS USED BECAUSE OF AN INCORRECT COMPOUND FILTER FACTOR OF RANGE PREDICATES
The compound filter factor of two range predicates on the same column is underestimated, that causes an inefficient access      2017-09-02

5.     PI83547: NON-MATCHING INDEX CHOSEN WHEN A MATCHING INDEX EXISTS
A non-matching index could be chosen when an index with good matching exists.    2017-09-02

6.     PI82634: MULTI INDEX ACCESS CHOSEN WHEN A BETTER MATCHING INDEX EXISTS
MULTI-INDEX ACCESS WAS CHOSEN WHEN A MORE EFFICIENT INDEX USING BETTER MATCHING EXISTS.       2017-08-02

7.     PI77792: ABSTRACT:INEFFICIENT ACCESS PATH WITH SORT DISTINCT IN CTE
AN INEFFICIENT ACCESS PATH CAN BE CHOSEN WHEN A SORT FOR DISTINCT IS NEEDED INSIDE A CTE.     2017-06-02

8.     PI73290: Db2 FOR Z/OS USERS OF QUERIES WITH GROUP BY, DISTINCT, IN SUBQUERY OR NOT IN SUBQUERY.
Db2 may choose an inefficient access path as non-matching index access without matching predicates and screening predicates when     2017-05-01

9.     PI73368: ABSTRACT=INEFFICIENT ACCESS PATH WITH SINGLE VALUE PAGE RANGE PREDICATE.An inefficient access path can be chosen when page range access is used for a join predicate and the columns has a cardinality 2017-05-01

10.    PI75966: INEFFICIENT ACCESS PATH IS SELECTED.
List prefetch plan with higher cost may be chosen mistakenly when there is one table in the query block and the index covers        2017-05-01

11.    PI71368: R-SCAN ACCESS PATH CHOSEN OVER MULTI-INDEX ACCESS FOR A TABLE WHICH QUALIFIES FOR NPGTHRSH BEHAVIOR
R-scan access path chosen over multi-index access for a table which qualifies for NPGTHRSH behavior.        2017-04-20

12.    PI75963: ACCESS PATH FOR A QUERY WITH GROUP BY AND ORDER BY CLAUSES INCLUDES AN UNNECESSARY SORT
For the following query the access path includes a sort although it is not necessary: 2017-04-20

13.    PI69349: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query    2017-04-14

14.    PI74019: DEFECT 40316 - TPCD (REVISTIT) QUERY #UV1B2 CL2 CPU REGRESSION IN V12
There is a regression for performance test. In V11, it could choose good access path, in V12, it chooses bad access path.   2017-04-03

15.    PI72887: INEFFICIENT ACCESS PATH WITH EARLY OUT
INEFFICIENT ACCESS PATH WITH EARLY OUT 2017-04-03

16.    PI71495: ABEND04E RC00E70005 AT DSNXGRDS DSNXOB2 M105 ON SQL STATEMENT WITH CONCENTRATE STATEMENTS WITH LITERALS
ABEND04E rc00e70005 at dsnxgrds dsnxob2 M105 in prepare SQL statement with attributes clause CONCENTRATE STATEMENTS WITH       2017-02-01

17.    PI72800: INCORRECT FILTER FACTOR FOR PARTITION KEY OF VOLATILE TABLE
Db2 may calculate a incorrect filter factor for using BETWEEN and RANGE predicates, when a volatile table is defined as 2017-02-01

18.    PI71110: FORWARDFIT OF PI70237
Performance problem when a user query choose R-scan in a single-table correlated subquery.    2017-02-01

19.    PI68238: SQLACCESSPATH OF THE ENTRY WITH LATEST TIMESTAMP AND ACCESSTYPE NR IS NOT SELECTED WHEN BIND PKG WITH OPTHINT ...
When BIND PACKAGE with OPTHINT and EXPLAIN(YES), the latest timestamp NR path will lost the chance to compete with other 2017-01-12

20.    PI68551: FF OF PI66289-INDEX WITH LESS MATCHING COLUMNS IS CHOSEN FOR INNER TABLE WHICH MAY CAUSE BAD PERFORMANCE
Index with less matching columns is chosen for inner table which may cause bad performance    2017-01-12

21.    PI69414: POOR SQL PERFORMANCE FOR MERGE STATEMENT
Poor SQL performance for MERGE statement       2017-01-03

22.    PI68086: ALLOW MORE TABLES TO BE ELIGIBLE FOR SPARSE INDEX ACCESS.
Due to a code bug, sometimes a table with very big non-correlated subquery (big means expensive in terms of elapsed    2016-12-01

 

Remove the filter for optimizer csects and you get 26:


1.     PI82797: LESS FILTERING INDEX SELECTED FOR INNER TABLE OF NESTED LOOP JOIN
A smaller, less filtering index is selected for the inner table with a Nested Loop Join.      2017-10-02

2.     PI78122: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-10-02

3.     PI83289: QUERY ACCESS PATH MAY BE UNPREDICTABLE FOR A QUERY WHERE THERE ARE EQUAL PREDICATES COVERING ALL THE COLUMNS ...
Query access path may be unpredictable for a query where there are equal predicates covering all the columns of a unique index.        2017-09-02

4.     PI83454: INEFFICIENT ACCESS PATH IS USED BECAUSE OF AN INCORRECT COMPOUND FILTER FACTOR OF RANGE PREDICATES
The compound filter factor of two range predicates on the same column is underestimated, that causes an inefficient access      2017-09-02

5.     PI83547: NON-MATCHING INDEX CHOSEN WHEN A MATCHING INDEX EXISTS
A non-matching index could be chosen when an index with good matching exists.    2017-09-02

6.     PI82634: MULTI INDEX ACCESS CHOSEN WHEN A BETTER MATCHING INDEX EXISTS
MULTI-INDEX ACCESS WAS CHOSEN WHEN A MORE EFFICIENT INDEX USING BETTER MATCHING EXISTS.       2017-08-02

7.     PI77792: ABSTRACT:INEFFICIENT ACCESS PATH WITH SORT DISTINCT IN CTE
AN INEFFICIENT ACCESS PATH CAN BE CHOSEN WHEN A SORT FOR DISTINCT IS NEEDED INSIDE A CTE.     2017-06-02

8.     PI73290: Db2 FOR Z/OS USERS OF QUERIES WITH GROUP BY, DISTINCT, IN SUBQUERY OR NOT IN SUBQUERY.
Db2 may choose an inefficient access path as non-matching index access without matching predicates and screening predicates when     2017-05-01

9.     PI75966: INEFFICIENT ACCESS PATH IS SELECTED.
List prefetch plan with higher cost may be chosen mistakenly when there is one table in the query block and the index covers        2017-05-01

10.    PI73368: ABSTRACT=INEFFICIENT ACCESS PATH WITH SINGLE VALUE PAGE RANGE PREDICATE.
An inefficient access path can be chosen when page range access is used for a join predicate and the columns has a cardinality 2017-05-01

11.    PI71368: R-SCAN ACCESS PATH CHOSEN OVER MULTI-INDEX ACCESS FOR A TABLE WHICH QUALIFIES FOR NPGTHRSH BEHAVIOR
R-scan access path chosen over multi-index access for a table which qualifies for NPGTHRSH behavior.        2017-04-20

12.    PI75963: ACCESS PATH FOR A QUERY WITH GROUP BY AND ORDER BY CLAUSES INCLUDES AN UNNECESSARY SORT
For the following query the access path includes a sort although it is not necessary: 2017-04-20

13.    PI67390: SQLCODE100 MAY OCCUR FOR SQL STATEMENTS USING LIST PREFETCH OR MULTI INDEX ACCESS
SQLCODE +100 may occur for sql statements using List Prefetch or multi index access    2017-04-14

14.    PI69349: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query    2017-04-14

15.    PI69054: TOTALENTRIES TRUNCATED IN RTS FOR LARGE LOAD RESULTS IN REBUILD INDEX FAILING
2.6 billion row table load is truncating totalentries in RTS.      2017-04-12

16.    PI74019: DEFECT 40316 - TPCD (REVISTIT) QUERY #UV1B2 CL2 CPU REGRESSION IN V12
There is a regression for performance test. In V11, it could choose good access path, in V12, it chooses bad access path.   2017-04-03

17.    PI76121: REMOTE CONNECTION ATTEMPT RESULTS IN NONMATCHING INDEX SCAN OF DSNFEX01 WHEN ROW FOR AUTHID IS MISSING FROM ...
Db2DDF See APAR PI71693 for Db2 11/10 for z/OS.       2017-04-03

18.    PI72887: INEFFICIENT ACCESS PATH WITH EARLY OUT
INEFFICIENT ACCESS PATH WITH EARLY OUT 2017-04-03

19.    PI71495: ABEND04E RC00E70005 AT DSNXGRDS DSNXOB2 M105 ON SQL STATEMENT WITH CONCENTRATE STATEMENTS WITH LITERALS
ABEND04E rc00e70005 at dsnxgrds dsnxob2 M105 in prepare SQL statement with attributes clause CONCENTRATE STATEMENTS WITH       2017-02-01

20.    PI72800: INCORRECT FILTER FACTOR FOR PARTITION KEY OF VOLATILE TABLE
Db2 may calculate a incorrect filter factor for using BETWEEN and RANGE predicates, when a volatile table is defined as 2017-02-01

21.    PI71110: FORWARDFIT OF PI70237
Performance problem when a user query choose R-scan in a single-table correlated subquery.    2017-02-01

22.    PI68238: SQLACCESSPATH OF THE ENTRY WITH LATEST TIMESTAMP AND ACCESSTYPE NR IS NOT SELECTED WHEN BIND PKG WITH OPTHINT ...
When BIND PACKAGE with OPTHINT and EXPLAIN(YES), the latest timestamp NR path will lost the chance to compete with other 2017-01-12

23.    PI68551: FF OF PI66289-INDEX WITH LESS MATCHING COLUMNS IS CHOSEN FOR INNER TABLE WHICH MAY CAUSE BAD PERFORMANCE
Index with less matching columns is chosen for inner table which may cause bad performance    2017-01-12

24.    PI69414: POOR SQL PERFORMANCE FOR MERGE STATEMENT
Poor SQL performance for MERGE statement       2017-01-03

25.    PI68086: ALLOW MORE TABLES TO BE ELIGIBLE FOR SPARSE INDEX ACCESS.
Due to a code bug, sometimes a table with very big non-correlated subquery (big means expensive in terms of elapsed    2016-12-01

26.    PI69029: REBIND APREUSESOURCE(PREVIOUS) IS NOT FINDING PREVIOUS ACCESSPATH WHEN USING PLANMGMT(BASIC)
When running this sample statement: REBIND PACKAGE(TEST.ABC00999.()) EXPLAIN(Y) -      2016-12-01

 

So we are talking about just over two per month…

 

Db2 11 APAR Review sqlaccesspath

Just drop the C10 and add B10 to the search and do it all again.


1.     PI78532: NON-MATCHING INDEX CHOSEN WHEN A MATCHING INDEX EXISTS 17/08/30 PTF PECHANGE
A non-matching index could be chosen when an index with good matching exists. 2017-08-30

2.     PI58411: INCORROUT CAN OCCUR FOR AN UPDATE QUERY USING TEMPORAL TABLES.
Temporal table has multiple indexes. One index to support the primary key constraint and one to support queries against the       2017-01-04

3.     PI62713: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query with LEFT OUTER JOIN and ORDER BY and also running with Sort     2016-11-02

4.     PI64779: SELECT DISTINCT RETURNS DUPLICATE VALUES.
Incorrect output can occur when the DISTINCT keyword is used, matching index access is used on the IN-list, but the IN-list   2016-10-03

5.     PI61893: INCORROUT WITH UPDATE STATEMENT AND CORRELATED SUBQUERY
A INCORROUT conditions occurs when a UPDATE statement is coded with a correlated subquery that contains a DISTINCT and FETCH     2016-08-02

 

Again, remove the yesHIPER and now there are 54:


1.     PI79438: INEFFICIENT ACCESS PATH FOR QUERY WITH MIN/MAX AND NO GROUP BY
An inefficient access path can be chosen when a query contains a MIN/MAX function with no Group BY.        2017-10-02

2.     PI84286: JOIN PREDICATE WITH CAST FUNCTION NON-INDEXABLE
A join predicate can become non-indexable if the predicate contains a decimal function without the length and scale    2017-10-02

3.     PI83769: AN INEFFICIENT INDEX CAN BE SELECTED TO PARTICIPATE IN MULTI-INDEX ACCESS
AN INEFFICIENT INDEX CAN BE SELECTED TO PARTICIPATE IN MULTI-INDEX ACCESS WHEN THERE IS A HIGH DEGREE OF UNCERTAINTY      2017-09-26

4.     PI82601: LESS FILTERING INDEX SELECTED FOR INNER TABLE OF NESTED LOOP JOIN
A smaller, less filtering index is selected for the inner table with a Nested Loop Join.      2017-09-02

5.     PI82772: INEFFICIENT ACCESS PATH IS USED BECAUSE OF AN INCORRECT COMPOUND FILTER FACTOR OF RANGE PREDICATES
The compound filter factor of two range predicates on the same column is underestimated, that causes an inefficient access      2017-09-02

6.     PI63607: INEFFICIENT ACCESS PATH COULD OCCUR WITH CARTESIAN JOIN
An inefficient access path could occur when the result of a Cartesian join does not produce better index matching on the      2017-08-30

7.     PI78532: NON-MATCHING INDEX CHOSEN WHEN A MATCHING INDEX EXISTS 17/08/30 PTF PECHANGE
A non-matching index could be chosen when an index with good matching exists.    2017-08-30

8.     PI79775: INDEX PROBING NOT BEING INVOKED
Under certain conditions, index probing is not being utilized for predicates that calculate a FF with no matching rows    2017-08-02

9.     PI80690: AE PI76369 FIX COMPLETION
AE PI76369 fix completion.        2017-07-05

10.    PI76369: ABSTRACT:INEFFICIENT ACCESS PATH WITH SORT DISTINCT IN CTE
AN INEFFICIENT ACCESS PATH CAN BE CHOSEN WHEN A SORT FOR DISTINCT IS NEEDED INSIDE A CTE.     2017-06-05

11.    PI75212: DURING AUTOBIND USING QUERYACCELERATION (ENABLE) BIND OPTION, STATIC QUERY IS BOUND FOR ACCELERATION ...
During AUTOBIND for a package bound QUERYACCELERATION(ENABLE), Db2 unexpectedly selects an IDAA access path and binds the query   2017-06-02

12.    PI59793: UNDERESTIMATED TOTAL INDEX FILTERING WITH PAGE RANGE SCREENING WHEN THE PAGE RANGE COLUMNS ARE NOT IN THE INDEX
An inaccurate IMFFADJ value will be generated in instances where when page range screening is performed and the columns used for      2017-05-03

13.    PI62376: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-04-11

14.    PI75342: ACCESS PATH FOR A QUERY WITH GROUP BY AND ORDER BY CLAUSES INCLUDES AN UNNECESSARY SORT.
For the following query the access path includes a sort although it is not necessary: 2017-04-03

15.    PI72177: INEFFICIENT ACCESS PATH IS SELECTED.
List prefetch plan with higher cost may be chosen mistakenly when there is one table in the query block and the index covers        2017-04-03

16.    PI70394: ABSTRACT=INEFFICIENT ACCESS PATH WITH SINGLE VALUE PAGE RANGE PREDICATE.
An inefficient access path can be chosen when page range access is used for a join predicate and the columns has a cardinality 2017-03-09

17.    PI73338: INEFFICIENT JOIN ACCESS ON PARTITIONED TABLE
Nested loop join may be chosen as the join type when hybrid join would likely have been a better choice.      2017-02-01

18.    PI66289: INDEX WITH LESS MATCHING COLUMNS IS CHOSEN FOR INNER TABLE WHICH MAY CAUSE BAD PERFORMANCE
Index with less matching columns is chosen for inner table which may cause bad performance    2017-01-12

19.    PI65041: SQLACCESSPATH OF THE ENTRY WITH LATEST TIMESTAMP AND ACCESSTYPE NR IS NOT SELECTED WHEN BIND PKG WITH OPTHINT ...
When BIND PACKAGE with OPTHINT and EXPLAIN(YES), the latest timestamp NR path will lost the chance to compete with other 2017-01-12

20.    PI58411: INCORROUT CAN OCCUR FOR AN UPDATE QUERY USING TEMPORAL TABLES.
Temporal table has multiple indexes. One index to support the primary key constraint and one to support queries against the       2017-01-04

21.    PI69685: ABEND04E RC00E70005 AT DSNXGRDS DSNXOB2 M105 ON AN SQL STATEMENT WITH ATTRIBUTE CONCENTRATE STATEMENTS WITH ...
ABEND04E rc00e70005 at dsnxgrds dsnxob2 M105 in a prepared SQL statement with prepared attributes clause CONCENTRATE STATEMENTS     2017-01-03

22.    PI71365: R-SCAN ACCESS PATH CHOSEN OVER MULTI-INDEX ACCESS FOR A TABLE WHICH QUALIFIES FOR NPGTHRSH BEHAVIOR
R-scan access path chosen over multi-index access for a table which qualifies for NPGTHRSH behavior.        2017-01-03

23.    PI68896: INCORRECT FILTER FACTOR FOR PARTITION KEY OF VOLATILE TABLE
Db2 may calculate a incorrect filter factor for using BETWEEN and RANGE predicates, when a volatile table is defined as 2017-01-03

24.    PI71415: POOR SQL PERFORMANCE WHEN THE ACCESS PATH USES NON-MATCHING INDEX FOR INDEX SKIPPING
Poor SQL Performance when the access path uses non-matching index for index skipping . 2017-01-03

25.    PI63541: INEFFICIENT ACCESS PATH WITH EARLY OUT
Ineffecient access path can be chosen when the access plan qualifies for index skipping but no index covers the join     2017-01-03

26.    PI68380: SUBOPTIMAL ACCESS PATH WITH A NESTED LOOP JOIN AND MULTI-INDEX ACCESS
A suboptimal access path is chosen when multi-index access is chosen as the inner table for a nested loop join. A hybrid join   2016-12-01

27.    PI67499: INEFFICIENT NON-MATCHING INDEX SCAN IS SELECTED WHEN THERE ARE MORE THAN 1 TABLES IN THE QUERY BLOCK WITH ...
Inefficient non-matching index scan is selected when when the query contains DISTINCT in the query and there are more than 1 2016-12-01

28.    PI70237: INEFFICIENT ACCESS PATH WHEN A QUERY HAS INSUBQ OR EXISTS-SUBQ AND THE SUBQUERY HAS A SINGLE TABLE
Inefficient access path when a query has INSUBQUERY or EXISTS-SUBQUERY and the subquery has a single table. Optimizer    2016-12-01

29.    PI66248: INEFFICIENT ACCESS PATH WHEN NESTED LOOP JOIN USED TO ACCESS A INNER MATERIALIZED QUERY BLOCK
An inefficient rscan access path for the inner table of a nested loop join when the the inner table is a materialized workfile.       2016-12-01

30.    PI64874: INDEX PROBING MAY ACCESS UNQUALIFIED PARTITION AT PREPARE TIME
Unqualified partitions are claimed by index probing at prepare time, that causes unnecessary locking issue and group buffer     2016-11-02

31.    PI62713: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query with LEFT OUTER JOIN and ORDER BY and also running with Sort     2016-11-02

32.    PI52204: INCORRECT DPSI LEAF PAGE ESTIMATION WHEN ALL THE PARTITION KEYS CONTAINS LOCAL PREDICATES
Inefficient access path is selected due to incorrect DPSI leaf page estimation when all the partition keys contains local 2016-10-03

33.    PI64779: SELECT DISTINCT RETURNS DUPLICATE VALUES.
Incorrect output can occur when the DISTINCT keyword is used, matching index access is used on the IN-list, but the IN-list   2016-10-03

34.    PI64234: INEFFICIENT ACCESS PATH INVOLVING RANGE LIST PREDICATE(S)
A Range list access path could be chosen when a more efficient access path is available.      2016-10-03

35.    PI64089: PERFORMANCE IMPACT WITH CTE SELECTED FROM A VIEW
When a CTE is defined in a view, a sub-optimal access path may occur. A optimal access path will be estimated for the CTE, and        2016-10-03

36.    PI61435: INCORRECT FILTER FACTOR MAY BE ASSIGNED FOR PAGE RANGE SCREENING PREDICATES WHEN PARTITION KEYS ARE DEFINED AS ...
Incorrect filter factor may be assigned for page range screening predicates when partition keys are defined as VARCHAR 2016-10-03

37.    PI60761: Enable NPGTHRSH for qualified partitions of a partitioned table based on partition level NPAGES.
The code to enable NPGTHRSH for qualified partitions of a partitioned table based on partition level stats (NPAGES)      2016-09-02

38.    PI61886: IN SUBQUERY FAILS TO MATCH ON INDEXABLE IN LIST COLUMN
For a query which contains an IN list on a subquery, Db2 currently will use the IN list column in an index match if the 2016-09-02

39.    PI60056: INEFFICIENT ACCESS PATH WITH AGGREGATE FUNCTIONS SELECT(MAX) OR SELECT(MIN).
Less than optimal performance is the result when the optimizer makes a inefficient access path decision when the aggregate       2016-08-02

40.    PI60333: UNNECESSARY SORT FOR ORDER BY WHEN DISTINCT/GROUP BY LIST COVERS A UNIQUE INDEX AND SELECTED INDEX SUPPORT ...
When a query contains an ORDER BY and DISTINCT/GROUP BY clause whose columns cover a unique index, Db2 selects an index with 2016-08-02

41.    PI61893: INCORROUT WITH UPDATE STATEMENT AND CORRELATED SUBQUERY
A INCORROUT conditions occurs when a UPDATE statement is coded with a correlated subquery that contains a DISTINCT and FETCH     2016-08-02

42.    PI60206: POOR SQL PERFORMANCE OF A QUERY THAT HAS A CORRELATED SUBQUERY COST REDUCTION
Poor SQL performance of a query that has a correlated subquery cost reduction . 2016-08-02

43.    PI59348: INEFFICIENT INDEX SELECTION FOR THE INNER TABLE OF A JOIN
Less than optimal performance is the result when the optimizer makes a inefficient index selection for the inner table of a   2016-07-15

44.    PI57513: GROUP BY/DISTINCT/MIN/MAX CLAUSES RESULT IN INCORRECT ACCESS PATH DUE TO INVALID COST REDUCTION
In V11, materialized work files which are used as the inner tables for left joins are being processed using a nested loop 2016-07-04

45.    PI61155: INCORRECT COMPOUND FILTER FACTOR ESTIMATION FOR TWO RANGE PREDICATES
Inefficient index is selected due to incorrect compound filter factor estimation for two range predicates. 2016-07-04

46.    PI50999: INCORRECT MATCHING FILTER FACTOR ESTIMATION FOR DPSI WHEN THE JOIN PREDICATES INVOLVE PARTITION KEY
Inefficient access path is used in a join or correlated subquery because IMFF of DPSI is not correctly estimated when the join       2016-06-02

47.    PI58329: INCORRECT VALUE IN QW0022RX FIELD FOR IFCID022 WHEN UNDER REOPT(ONCE) OR REOPT(AUTO)
Incorrect value in QW0022RX field for IFCID022 when under REOPT ONCE OR REOPT AUTO .   2016-05-04

48.    PI53774: INEFFICIENT ACCESS PATH CHOSEN WHEN Db2 INCORRECTLY ESTIMATES THE FILTERING WHEN COMBINING TWO RANGE ...
Inefficient access path may be chosen when Db2 incorrectly estimates the filtering when combining two range predicates into      2016-04-05

49.    PI54988: OPTIMAL INDEX ACCESS MAY NOT BE USED WHEN STATISTICS IS NOT COLLECTED
Optimal index access may not be used when statistics is not collected.    2016-04-05

50.    PI44963: INCORRECT COST ESTIMATION FOR I1 INDEX SCAN
Cost estimation in DSN_STATEMNT_TABLE is very high for one-fetch index scan(I1). Prefetch method is 'D' in the   2016-03-10

51.    PI53790: INCORRECT ACCESS PATH CHOSEN FOR OPTIMIZE FOR 1 ROW
Db2 is producing an incorrect and inefficient access path in V11 when the OPTIMIZE FOR 1 ROW clause is added to a query which 2016-03-02

52.    PI50063: AN INACCURATE COMPOUND FILTER FACTOR MAY BE PRODUCED FOR A PREDICATE WITH AN OR CLAUSE
AN INACCURATE COMPOUND FILTER FACTOR MAY BE PRODUCED FOR A PREDICATE WITH AN OR CLAUSE 2016-02-01

53.    PI49507: DIFFERENT ACCESS PATH IS USED WHEN QUERY ON VIEW INSTEAD OF BASE TABLE.
A view is directly created on a base table. SQL statement on the view should be equivalent to the SQL on the base table. 2016-02-01

54.    PI49557: INEFFICIENT ACCESS PATH FOR QUERY WITH FUNCTION MIN OR MAX BY INCORRECT REDUCTION FOR EARLY OUT
Inefficient access path for query with function MIN or MAX by incorrect reduction for early out        2016-01-04

 

Remove the filter for optimizer csects and you get 56:


1.     PI79438: INEFFICIENT ACCESS PATH FOR QUERY WITH MIN/MAX AND NO GROUP BY
An inefficient access path can be chosen when a query contains a MIN/MAX function with no Group BY.        2017-10-02

2.     PI84286: JOIN PREDICATE WITH CAST FUNCTION NON-INDEXABLE
A join predicate can become non-indexable if the predicate contains a decimal function without the length and scale    2017-10-02

3.     PI83769: AN INEFFICIENT INDEX CAN BE SELECTED TO PARTICIPATE IN MULTI-INDEX ACCESS
AN INEFFICIENT INDEX CAN BE SELECTED TO PARTICIPATE IN MULTI-INDEX ACCESS WHEN THERE IS A HIGH DEGREE OF UNCERTAINTY      2017-09-26

4.     PI86573: BETTER MATCHING INDEX NOT CHOSEN WHEN COMPETING INDEXES CONTAIN A SUBSET OF THE SAME COLUMNS.
A better matching index can be overlooked when the competing indexes share a set of the same columns.        2017-09-21

5.     PI82772: INEFFICIENT ACCESS PATH IS USED BECAUSE OF AN INCORRECT COMPOUND FILTER FACTOR OF RANGE PREDICATES
The compound filter factor of two range predicates on the same column is underestimated, that causes an inefficient access      2017-09-02

6.     PI82601: LESS FILTERING INDEX SELECTED FOR INNER TABLE OF NESTED LOOP JOIN
A smaller, less filtering index is selected for the inner table with a Nested Loop Join.      2017-09-02

7.     PI78532: NON-MATCHING INDEX CHOSEN WHEN A MATCHING INDEX EXISTS 17/08/30 PTF PECHANGE
A non-matching index could be chosen when an index with good matching exists.    2017-08-30

8.     PI63607: INEFFICIENT ACCESS PATH COULD OCCUR WITH CARTESIAN JOIN
An inefficient access path could occur when the result of a Cartesian join does not produce better index matching on the      2017-08-30

9.     PI79775: INDEX PROBING NOT BEING INVOKED
Under certain conditions, index probing is not being utilized for predicates that calculate a FF with no matching rows    2017-08-02

10.    PI80690: AE PI76369 FIX COMPLETION
AE PI76369 fix completion.        2017-07-05

11.    PI76369: ABSTRACT:INEFFICIENT ACCESS PATH WITH SORT DISTINCT IN CTE
AN INEFFICIENT ACCESS PATH CAN BE CHOSEN WHEN A SORT FOR DISTINCT IS NEEDED INSIDE A CTE.     2017-06-05

12.    PI75212: DURING AUTOBIND USING QUERYACCELERATION (ENABLE) BIND OPTION, STATIC QUERY IS BOUND FOR ACCELERATION ...
During AUTOBIND for a package bound QUERYACCELERATION(ENABLE), Db2 unexpectedly selects an IDAA access path and binds the query   2017-06-02

13.    PI59793: UNDERESTIMATED TOTAL INDEX FILTERING WITH PAGE RANGE SCREENING WHEN THE PAGE RANGE COLUMNS ARE NOT IN THE INDEX
An inaccurate IMFFADJ value will be generated in instances where when page range screening is performed and the columns used for      2017-05-03

14.    PI62376: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-04-11

15.    PI75342: ACCESS PATH FOR A QUERY WITH GROUP BY AND ORDER BY CLAUSES INCLUDES AN UNNECESSARY SORT.
For the following query the access path includes a sort although it is not necessary: 2017-04-03

16.    PI72177: INEFFICIENT ACCESS PATH IS SELECTED.
List prefetch plan with higher cost may be chosen mistakenly when there is one table in the query block and the index covers        2017-04-03

17.    PI70394: ABSTRACT=INEFFICIENT ACCESS PATH WITH SINGLE VALUE PAGE RANGE PREDICATE.
An inefficient access path can be chosen when page range access is used for a join predicate and the columns has a cardinality 2017-03-09

18.    PI73338: INEFFICIENT JOIN ACCESS ON PARTITIONED TABLE
Nested loop join may be chosen as the join type when hybrid join would likely have been a better choice.      2017-02-01

19.    PI66289: INDEX WITH LESS MATCHING COLUMNS IS CHOSEN FOR INNER TABLE WHICH MAY CAUSE BAD PERFORMANCE
Index with less matching columns is chosen for inner table which may cause bad performance    2017-01-12

20.    PI65041: SQLACCESSPATH OF THE ENTRY WITH LATEST TIMESTAMP AND ACCESSTYPE NR IS NOT SELECTED WHEN BIND PKG WITH OPTHINT ...
When BIND PACKAGE with OPTHINT and EXPLAIN(YES), the latest timestamp NR path will lost the chance to compete with other 2017-01-12

21.    PI58411: INCORROUT CAN OCCUR FOR AN UPDATE QUERY USING TEMPORAL TABLES.
Temporal table has multiple indexes. One index to support the primary key constraint and one to support queries against the       2017-01-04

22.    PI69685: ABEND04E RC00E70005 AT DSNXGRDS DSNXOB2 M105 ON AN SQL STATEMENT WITH ATTRIBUTE CONCENTRATE STATEMENTS WITH ...
ABEND04E rc00e70005 at dsnxgrds dsnxob2 M105 in a prepared SQL statement with prepared attributes clause CONCENTRATE STATEMENTS     2017-01-03

23.    PI71365: R-SCAN ACCESS PATH CHOSEN OVER MULTI-INDEX ACCESS FOR A TABLE WHICH QUALIFIES FOR NPGTHRSH BEHAVIOR
R-scan access path chosen over multi-index access for a table which qualifies for NPGTHRSH behavior.        2017-01-03

24.    PI68896: INCORRECT FILTER FACTOR FOR PARTITION KEY OF VOLATILE TABLE
Db2 may calculate a incorrect filter factor for using BETWEEN and RANGE predicates, when a volatile table is defined as 2017-01-03

25.    PI71415: POOR SQL PERFORMANCE WHEN THE ACCESS PATH USES NON-MATCHING INDEX FOR INDEX SKIPPING
Poor SQL Performance when the access path uses non-matching index for index skipping . 2017-01-03

26.    PI63541: INEFFICIENT ACCESS PATH WITH EARLY OUT
Ineffecient access path can be chosen when the access plan qualifies for index skipping but no index covers the join     2017-01-03

27.    PI68380: SUBOPTIMAL ACCESS PATH WITH A NESTED LOOP JOIN AND MULTI-INDEX ACCESS
A suboptimal access path is chosen when multi-index access is chosen as the inner table for a nested loop join. A hybrid join   2016-12-01

28.    PI67499: INEFFICIENT NON-MATCHING INDEX SCAN IS SELECTED WHEN THERE ARE MORE THAN 1 TABLES IN THE QUERY BLOCK WITH ...
Inefficient non-matching index scan is selected when when the query contains DISTINCT in the query and there are more than 1 2016-12-01

29.    PI70237: INEFFICIENT ACCESS PATH WHEN A QUERY HAS INSUBQ OR EXISTS-SUBQ AND THE SUBQUERY HAS A SINGLE TABLE
Inefficient access path when a query has INSUBQUERY or EXISTS-SUBQUERY and the subquery has a single table. Optimizer    2016-12-01

30.    PI66248: INEFFICIENT ACCESS PATH WHEN NESTED LOOP JOIN USED TO ACCESS A INNER MATERIALIZED QUERY BLOCK
An inefficient rscan access path for the inner table of a nested loop join when the the inner table is a materialized workfile.       2016-12-01

31.    PI64874: INDEX PROBING MAY ACCESS UNQUALIFIED PARTITION AT PREPARE TIME
Unqualified partitions are claimed by index probing at prepare time, that causes unnecessary locking issue and group buffer     2016-11-02

32.    PI62713: INCORROUT WITH SQLSTATE 01003 OCCURRED FOR A QUERY WITH LEFT OUTER JOIN AND ORDER BY AND ALSO RUNNING WITH ...
incorrout (wrong data) with SQLSTATE 01003 occurred for a query with LEFT OUTER JOIN and ORDER BY and also running with Sort     2016-11-02

33.    PI52204: INCORRECT DPSI LEAF PAGE ESTIMATION WHEN ALL THE PARTITION KEYS CONTAINS LOCAL PREDICATES
Inefficient access path is selected due to incorrect DPSI leaf page estimation when all the partition keys contains local 2016-10-03

34.    PI64234: INEFFICIENT ACCESS PATH INVOLVING RANGE LIST PREDICATE(S)
A Range list access path could be chosen when a more efficient access path is available.      2016-10-03

35.    PI64779: SELECT DISTINCT RETURNS DUPLICATE VALUES.
Incorrect output can occur when the DISTINCT keyword is used, matching index access is used on the IN-list, but the IN-list   2016-10-03

36.    PI64089: PERFORMANCE IMPACT WITH CTE SELECTED FROM A VIEW
When a CTE is defined in a view, a sub-optimal access path may occur. A optimal access path will be estimated for the CTE, and        2016-10-03

37.    PI61435: INCORRECT FILTER FACTOR MAY BE ASSIGNED FOR PAGE RANGE SCREENING PREDICATES WHEN PARTITION KEYS ARE DEFINED AS ...
Incorrect filter factor may be assigned for page range screening predicates when partition keys are defined as VARCHAR 2016-10-03

38.    PI60761: Enable NPGTHRSH for qualified partitions of a partitioned table based on partition level NPAGES.
The code to enable NPGTHRSH for qualified partitions of a partitioned table based on partition level stats (NPAGES)      2016-09-02

39.    PI61886: IN SUBQUERY FAILS TO MATCH ON INDEXABLE IN LIST COLUMN
For a query which contains an IN list on a subquery, Db2 currently will use the IN list column in an index match if the 2016-09-02

40.    PI60056: INEFFICIENT ACCESS PATH WITH AGGREGATE FUNCTIONS SELECT(MAX) OR SELECT(MIN).
Less than optimal performance is the result when the optimizer makes a inefficient access path decision when the aggregate       2016-08-02

41.    PI60333: UNNECESSARY SORT FOR ORDER BY WHEN DISTINCT/GROUP BY LIST COVERS A UNIQUE INDEX AND SELECTED INDEX SUPPORT ...
When a query contains an ORDER BY and DISTINCT/GROUP BY clause whose columns cover a unique index, Db2 selects an index with 2016-08-02

42.    PI61893: INCORROUT WITH UPDATE STATEMENT AND CORRELATED SUBQUERY
A INCORROUT conditions occurs when a UPDATE statement is coded with a correlated subquery that contains a DISTINCT and FETCH     2016-08-02

43.    PI60206: POOR SQL PERFORMANCE OF A QUERY THAT HAS A CORRELATED SUBQUERY COST REDUCTION
Poor SQL performance of a query that has a correlated subquery cost reduction . 2016-08-02

44.    PI59348: INEFFICIENT INDEX SELECTION FOR THE INNER TABLE OF A JOIN
Less than optimal performance is the result when the optimizer makes a inefficient index selection for the inner table of a   2016-07-15

45.    PI54868: PERFORMANCE DEGRADATION WITH PAGE RANGE FILTERING ON A JOIN PREDICATE AND NO LOCAL PREDICATES
Db2 is not estimating the correct index filtering when page range filtering is available on a join predicate and no local     2016-07-12

46.    PI57513: GROUP BY/DISTINCT/MIN/MAX CLAUSES RESULT IN INCORRECT ACCESS PATH DUE TO INVALID COST REDUCTION
In V11, materialized work files which are used as the inner tables for left joins are being processed using a nested loop 2016-07-04

47.    PI61155: INCORRECT COMPOUND FILTER FACTOR ESTIMATION FOR TWO RANGE PREDICATES
Inefficient index is selected due to incorrect compound filter factor estimation for two range predicates. 2016-07-04

48.    PI50999: INCORRECT MATCHING FILTER FACTOR ESTIMATION FOR DPSI WHEN THE JOIN PREDICATES INVOLVE PARTITION KEY
Inefficient access path is used in a join or correlated subquery because IMFF of DPSI is not correctly estimated when the join       2016-06-02

49.    PI58329: INCORRECT VALUE IN QW0022RX FIELD FOR IFCID022 WHEN UNDER REOPT(ONCE) OR REOPT(AUTO)
Incorrect value in QW0022RX field for IFCID022 when under REOPT ONCE OR REOPT AUTO .   2016-05-04

50.    PI53774: INEFFICIENT ACCESS PATH CHOSEN WHEN Db2 INCORRECTLY ESTIMATES THE FILTERING WHEN COMBINING TWO RANGE ...
Inefficient access path may be chosen when Db2 incorrectly estimates the filtering when combining two range predicates into      2016-04-05

51.    PI54988: OPTIMAL INDEX ACCESS MAY NOT BE USED WHEN STATISTICS IS NOT COLLECTED
Optimal index access may not be used when statistics is not collected.    2016-04-05

52.    PI44963: INCORRECT COST ESTIMATION FOR I1 INDEX SCAN
Cost estimation in DSN_STATEMNT_TABLE is very high for one-fetch index scan(I1). Prefetch method is 'D' in the   2016-03-10

53.    PI53790: INCORRECT ACCESS PATH CHOSEN FOR OPTIMIZE FOR 1 ROW
Db2 is producing an incorrect and inefficient access path in V11 when the OPTIMIZE FOR 1 ROW clause is added to a query which 2016-03-02

54.    PI50063: AN INACCURATE COMPOUND FILTER FACTOR MAY BE PRODUCED FOR A PREDICATE WITH AN OR CLAUSE
AN INACCURATE COMPOUND FILTER FACTOR MAY BE PRODUCED FOR A PREDICATE WITH AN OR CLAUSE 2016-02-01

55.    PI49507: DIFFERENT ACCESS PATH IS USED WHEN QUERY ON VIEW INSTEAD OF BASE TABLE.
A view is directly created on a base table. SQL statement on the view should be equivalent to the SQL on the base table. 2016-02-01

56.    PI49557: INEFFICIENT ACCESS PATH FOR QUERY WITH FUNCTION MIN OR MAX BY INCORRECT REDUCTION FOR EARLY OUT
Inefficient access path for query with function MIN or MAX by incorrect reduction for early out        2016-01-04

 

So we are still talking about just over two per month…

 

Db2 10 APAR Review sqlaccesspath

Just drop the B10 and add A10 to the search and do it all again.


1.     PI49116: TOTALENTRIES TRUNCATED IN RTS FOR LARGE LOAD RESULTS IN REBUILD INDEX FAILING
2.6 billion row table load is truncating totalentries in RTS.                                                         2016-12-01

2.     PI66401: POOR PERF FOR XMLTABLE FUNCTION WITH PREDICATE BEING PUSHED INSIDE XPATH PRODUCES LOOSE HIGH KEY VALUE FOR ...
The XMLTABLE function is producing a loose high key value for MSIKEYP2 when searching for a specific docid.           2016-12-01

3.     PI15740: INCORROUT DUPLICATED RECORDS RETURNED FOR QUERY WITH SQLACCESSPATH OF RANGELIST
The problem can happen when 1) range list access is used,                                                            2016-01-30

Again, remove the yesHIPER and now there are 16 APARs

 


1.     PI85418: PREPARE TAKES LONG TIME AND HIGH CPU IF THE QUERY CONTAINS MANY OR PREDICATES WHICH MAY QUALIFY RANGE LIST ...
A complex query contains many OR predicates that potentially qualifies range list access(ACCESSTYPE=NR), the prepare of the      2017-09-25

2.     PI76372: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-05-01

3.     PI49116: TOTALENTRIES TRUNCATED IN RTS FOR LARGE LOAD RESULTS IN REBUILD INDEX FAILING
2.6 billion row table load is truncating totalentries in RTS.      2016-12-01

4.     PI66135: INEFFICIENT INDEX MAY BE SELECTED
An inefficient index may be chosen by the optimizer when certain levels of uncertainly exist on some predicates. 2016-12-01

5.     PI66401: POOR PERF FOR XMLTABLE FUNCTION WITH PREDICATE BEING PUSHED INSIDE XPATH PRODUCES LOOSE HIGH KEY VALUE FOR ...
The XMLTABLE function is producing a loose high key value for MSIKEYP2 when searching for a specific docid.       2016-12-01

6.     PI58274: Inefficient access path for a query with OPTIMIZE FOR 1 ROW or FETCH FIRST 1 ROW when an inner index matches ...
When the outer composite is guaranteed to be a single row and OPTIMIZE FOR 1 ROW or FETCH FIRST 1 ROW is specified, Db2 is not   2016-07-04

7.     PI59200: AN INDEX WITH LESS MATCHING COLUMN IS USED WHEN QUERY CONTAINS IN LIST PREDICATE
Optimal index may not be used for below query, SELECT * FROM TB1   2016-07-04

8.     PI39053: CLAIM ACQUIRE FOR SET STATEMENTS AGAINST SYSTSTAB RESULTS IN DSNT501I RC00C200EA DURING CATALOG REORG
Claim acquire for SET statements against SYSTSTAB results in DSNT501I RC00C200EA during Db2 CATALOG REORG 2016-05-19

9.     PI54892: DIFFERENT ACCESS PATH IS USED DUE TO A TIMING ISSUE IN OPTIMIZER
Different access path is used due to a timing issue in optimizer. 2016-05-04

10.    PI53633: PERFORMANCE IMPACT WHEN DSNZPARM MAXRBLK IS SET GREATER THAN ACCEPTABLE VALUE
When MAXRBLK is set to a value of 16777216 or higher, the run time evaluation will be incorrect with the threshold       2016-05-04

11.    PI57655: DIRECT ROW ACCESS IS DEFEATED WHEN THE QUERY HAS FFNR
Poor performance due to Direct Row Access through ROWID column being degraded to index/tablespace scan when the query has a 2016-05-04

12.    PI54978: MERGE STATEMENT USES DEFAULT TABLE CARDINALITY WHEN CARDINALITY IS PROVIDED VIA THE "FOR N ROWS" CLAUSE
The merge statement uses the default table cardinality of 10000 when the cardinality is provided via the "FOR n ROWS" clause.   2016-05-04

13.    PI56300: POOR BIND PERFORMANCE MAY OCCUR DUE TO UNNECESSARY ACCESS TO PLAN_TABLE WHEN SET STATEMENT IS APPLIED
Poor bind performance may occur due to unnecessary access to PLAN_TABLE when SET statement is applied.     2016-04-05

14.    PI49018: ACCESS PATH ENHANCEMENT FOR A QUERY CONTAINING A JOIN PREDICATE ON A TABLE WITH DEFAULT COLUMN CARDINALITY ...
Db2 recognizes cases in which an ordered outer table can provide benefit on access to the inner table. When the outer table is    2016-03-02

15.    PI53169: POOR SQL PERFORMANCE WHEN RANGE LIST ACCESS IS USED AND PTF UI22717 IS APPLIED 15/11/25 PTF PECHANGE
Poor SQL performance when range list access is used and PTF UI22717 is applied .       2016-03-02

16.    PI15740: INCORROUT DUPLICATED RECORDS RETURNED FOR QUERY WITH SQLACCESSPATH OF RANGELIST
The problem can happen when 1) range list access is used,   2016-01-30

 

Remove the filter for optimizer csects and you get 17:


1.     PI85418: PREPARE TAKES LONG TIME AND HIGH CPU IF THE QUERY CONTAINS MANY OR PREDICATES WHICH MAY QUALIFY RANGE LIST ...
A complex query contains many OR predicates that potentially qualifies range list access(ACCESSTYPE=NR), the prepare of the      2017-09-25

2.     PI76372: INEFFICIENT ACCESS PATH CHOSEN WHEN NO MATCHING INDEX EXISTS TO SATISFY THE JOIN PREDICATE.
An inefficient access path can be selected for a query with no matching index to cover the join predicate.   2017-05-01

3.     PI71693: REMOTE CONNECTION ATTEMPT RESULTS IN NONMATCHING INDEX SCAN OF DSNFEX01 WHEN ROW FOR AUTHID IS MISSING FROM ...
Db2DDF See APAR PI76121 for Db2 12 for z/OS.   2017-03-02

4.     PI49116: TOTALENTRIES TRUNCATED IN RTS FOR LARGE LOAD RESULTS IN REBUILD INDEX FAILING
2.6 billion row table load is truncating totalentries in RTS.      2016-12-01

5.     PI66135: INEFFICIENT INDEX MAY BE SELECTED
An inefficient index may be chosen by the optimizer when certain levels of uncertainly exist on some predicates. 2016-12-01

6.     PI66401: POOR PERF FOR XMLTABLE FUNCTION WITH PREDICATE BEING PUSHED INSIDE XPATH PRODUCES LOOSE HIGH KEY VALUE FOR ...
The XMLTABLE function is producing a loose high key value for MSIKEYP2 when searching for a specific docid.       2016-12-01

7.     PI58274: Inefficient access path for a query with OPTIMIZE FOR 1 ROW or FETCH FIRST 1 ROW when an inner index matches ...
When the outer composite is guaranteed to be a single row and OPTIMIZE FOR 1 ROW or FETCH FIRST 1 ROW is specified, Db2 is not   2016-07-04

8.     PI59200: AN INDEX WITH LESS MATCHING COLUMN IS USED WHEN QUERY CONTAINS IN LIST PREDICATE
Optimal index may not be used for below query, SELECT * FROM TB1   2016-07-04

9.     PI39053: CLAIM ACQUIRE FOR SET STATEMENTS AGAINST SYSTSTAB RESULTS IN DSNT501I RC00C200EA DURING CATALOG REORG
Claim acquire for SET statements against SYSTSTAB results in DSNT501I RC00C200EA during Db2 CATALOG REORG 2016-05-19

10.    PI54892: DIFFERENT ACCESS PATH IS USED DUE TO A TIMING ISSUE IN OPTIMIZER
Different access path is used due to a timing issue in optimizer. 2016-05-04

11.    PI53633: PERFORMANCE IMPACT WHEN DSNZPARM MAXRBLK IS SET GREATER THAN ACCEPTABLE VALUE
When MAXRBLK is set to a value of 16777216 or higher, the run time evaluation will be incorrect with the threshold       2016-05-04

12.    PI57655: DIRECT ROW ACCESS IS DEFEATED WHEN THE QUERY HAS FFNR
Poor performance due to Direct Row Access through ROWID column being degraded to index/tablespace scan when the query has a 2016-05-04

13.    PI54978: MERGE STATEMENT USES DEFAULT TABLE CARDINALITY WHEN CARDINALITY IS PROVIDED VIA THE "FOR N ROWS" CLAUSE
The merge statement uses the default table cardinality of 10000 when the cardinality is provided via the "FOR n ROWS" clause.   2016-05-04

14.    PI56300: POOR BIND PERFORMANCE MAY OCCUR DUE TO UNNECESSARY ACCESS TO PLAN_TABLE WHEN SET STATEMENT IS APPLIED
Poor bind performance may occur due to unnecessary access to PLAN_TABLE when SET statement is applied.     2016-04-05

15.    PI49018: ACCESS PATH ENHANCEMENT FOR A QUERY CONTAINING A JOIN PREDICATE ON A TABLE WITH DEFAULT COLUMN CARDINALITY ...
Db2 recognizes cases in which an ordered outer table can provide benefit on access to the inner table. When the outer table is    2016-03-02

16.    PI53169: POOR SQL PERFORMANCE WHEN RANGE LIST ACCESS IS USED AND PTF UI22717 IS APPLIED 15/11/25 PTF PECHANGE
Poor SQL performance when range list access is used and PTF UI22717 is applied .       2016-03-02

17.    PI15740: INCORROUT DUPLICATED RECORDS RETURNED FOR QUERY WITH SQLACCESSPATH OF RANGELIST
The problem can happen when 1) range list access is used,   2016-01-30

So we are still talking about just over one per month, which implies that Db2 10 was “more stable” in this area. To be fair, Db2 10 is a lot older (GA date 2010-10-22) than 11 and 12 so I am not surprised that after seven years the bug rate is dropping off!

What does all this mean?

What it means to me, is that just looking at sqlaccesspath shows a pretty high turnover rate that must be tested. There are HIPERs in here that could really hurt, and so applying maintenance, especially now in the Agile Db2 12 world, becomes even more critical to your business.

Are you ready for this?


More about : Db2 12 SQL access paths; Agile, SQL Codes/Catalog/Function Levels


See also our CDDC tool suite: Continuous Delivery – Deployment Check

CDDC Supports fully automated testing of the new Db2 agile delivery:

– BIF/ICI Detection: Checks incompatibilities on FUNCTION LEVEL
– Access Path PreCheck
– Creates quality environments from a production clone
– Capture the entire workload incl. DCL, DDL, commands…


 

As usual, if you have any comments or queries please feel free to drop me a line!

TTFN

Roy Boxwell