PH21370: INITIAL ZPARMS SIMPLIFICATION ENHANCEMENTS

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Initial zparms simplification enhancements
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All Db2 12 for z/OS customers.                               *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * This APAR provides updated ranges and                        *
  * default settings for selected Db2 12                         *
  * subsystem (DSNZPxxx) parameters.                             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A review of Db2 subsystem parameters reveals some that accept
  settings or have default settings that do not comply with Db2
  best practices:
  CHKFREQ - specifies, when single checkpoint mode is in
  effect, either the number of log records written between
  checkpoints (if 1000 - 16000000) or the number of minutes
  between checkpoints (if 1 to 60).  Current good practice
  for time-oriented checkpoint intervals is to take a
  checkpoint at least every 3 minutes.  The current CHKFREQ
  default of 5 minutes does not agree with the best practice
  of taking a checkpoint every 3 minutes.
  CHKMINS - specifies, when dual checkpoint mode is in
  effect, the number of minutes between checkpoints (1 to
  1439).  Current good practice for time-oriented checkpoint
  intervals is to take a checkpoint at least every 5 minutes.
  PCLOSET - specifies the number of minutes that a partition
  or page set remains read-write after it is updated and
  before it is converted to read-only.  The current default
  setting is 10 minutes but Db2 best practice is 45 minutes.
  MAXRBLK - specifies the amount of storage in kilobytes that
  is needed for the RID pool.  The current default setting is
  400000 KB but with todays greater data volume and increased
  storage availability, the Db2 best practice is 1000000 KB.
  NPGTHRSH - specifies whether Db2 favors matching index
  access, through the index with the most matching columns,
  for tables or partitions that have fewer data pages than the
  specified value.  The current default of 0 means that Db2
  always chooses the access path based on cost estimates,
  regardless of the number of data pages that statistics
  indicate for the table or partition.  However, Db2
  recommends use of NPGTHRSH=1 so that matching index access
  can be chosen when statistics for a table space or partition
  show that it is empty or when statistics show the default.
  INLISTP - the maximum number of elements in an IN-list for
  certain IN predicate optimizations to occur.  The current
  default of 50 elements does not reflect the current best
  practice recommendation of 1000.
  The sample DSNTIJUZ job in prefix.SDSNSAMP(DSNTIJUZ)
  contains an extraneous continuation character 'X' in column
  72 following the keyword parameter XML_RANDOMIZE_DOCID=NO.
  This issue does not affect DSNTIJUZ jobs that have been
  edited by the Db2 installation CLIST.
  

Problem conclusion

Temporary fix

Comments

• **************************************
  In response, this APAR updates the default setting - or in
  some cases the range of acceptable settings - of each the
  following parameters:
  CHKFREQ - The default setting is changed from 5 minutes to 3.
  Also, values from 6 to 60 minutes are no longer documented
  as valid and are no longer accepted by the MINUTES/CHECKPOINT
  field on installation panel DSNTIPL1 when the CHECKPOINT TYPE
  field is set to MINUTES.  When CHKTYPE=SINGLE, DSN6SYSP still
  accepts CHKFREQ values from 6 to 60 for compatibility reasons
  but converts them to 5, writes the following message during
  assembly, and sets the minimum return code to 4: 'CHKFREQ WAS
  DECREASED FROM n TO 5, THE MAXIMUM CHECKPOINT SETTING IN
  MINUTES' where 'n' is the specified CHKFREQ setting.
  CHKMINS - Values from 6 to 1439 minutes are no longer
  documented as valid and are no longer accepted by the
  MINUTES/CHECKPOINT field on installation panel DSNTIPL1 when
  the CHECKPOINT TYPE field is set to BOTH.  When CHKTYPE=BOTH,
  DSN6SYSP still accepts values from 6 to 1439 for
  compatibility reasons but converts them to 5, writes the
  following message during assembly, and sets the minimum
  return code to 4:
  'CHKMINS WAS DECREASED FROM n TO 5, THE MAXIMUM CHECKPOINT
  SETTING IN MINUTES' where 'n' is the specified CHKMINS
  setting.
  PCLOSET - The default setting is changed from 10 minutes to
  the Db2 best-practices value of 45.
  MAXRBLK - The default setting is changed from 400000
  kilobytes to the Db2 best-practices value of 1000000
  kilobytes.
  NPGTHRSH - The default setting is changed from 0 to the Db2
  best-practices value of 1.
  INLISTP - The default setting is changed from 50 to the Db2
  best-practices value of 1000.
  Review your current Db2 subsystem parameter settings with
  respect to the above changes to determine if you should
  update your current settings to comply with Db2 good
  practice recommendations.
  Applying the PTF for this APAR does not directly modify your
  Db2 configuration.  However, it will be affected the next
  time you rebuild your subsystem parameter (DSNZPxxx) module
  if you specify one or more of the following parameters in
  the ranges indicated:
  CHKFREQ in the range of 6 to 60 (when CHKTYPE=SINGLE): These
  settings will be converted to 5 during subsystem parameter
  assembly with the warning message noted above.  Following
  the next use of the -SET SYSPARM command or Db2 restart, Db2
  will take more frequent checkpoints than previously.
  CHKMINS in the range of 6 to 1439 (when CHKTYPE=BOTH): These
  settings will be converted to 5 during subsystem parameter
  assembly with the warning message noted above.  Following
  the next use of the -SET SYSPARM command or Db2 restart, Db2
  will take more frequent checkpoints than previously.
  This APAR also modifies the sample DSNTIJUZ job in
  prefix.SDSNSAMP to remove the extraneous continuation
  character 'X' in column 72 after the keyword parameter
  XML_RANDOMIZE_DOCID=NO.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UI68424

Modules/Macros

• DSN6SPRM DSNTIPL1 DSNTXAZP DSN6SYSP DSNTIDXA DSNTIJUZ DSNTINST
  DSNTIDXC DSNTIDXB DSN@XAZP
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RC10 PSY UI68424

     UP20/03/25 P F003

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.