PH65562: NEW FUNCTION FOR PSEUDO CLOSE

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Pseudo close new function
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Db2 13 for z/OS data sharing users.      *
  ****************************************************************
  * PROBLEM DESCRIPTION: APAR PH65562 provides refresh prefetch  *
  *                      solution for cross invalidated pages    *
  *                      and introduces the capability to        *
  *                      specify the pseudo close interval for   *
  *                      a specific buffer pool.                 *
  ****************************************************************
  Db2 automatically converts updated page sets or partitions
  from read-write intent to read-only intent state, which is
  controlled by the pseudo-close mechanism using the pseudo-close
  intervals (subsystem parameter, DSN6SYSP PCLOSET value).
  Conversion takes place when elapsed time since a page set or
  partition was last updated exceeds the time specified in
  PCLOSET. The page set or partition becomes non GBP-dependent
  and the pages in local buffer pools are cross-invalidated.
  Thereafter when read-write activity starts again, the
  page set / partition switches in to GBP dependency and the
  pages in the buffer pools are cross-invalidated again. This
  repeated invalidation behavior because of going in and out of
  GBP-dependency is painful for the business-critical
  applications that depend on large indexes which are expected
  to be in memory mostly. This invalidation behavior may defeat
  the purpose of having large buffer pools and increase
  SYNCREADs impacting online workload performance.
  

Problem conclusion

Temporary fix

Comments

• In this APAR, for buffer pools with PGSTEAL(LRU/FIFO), in
  order to address the issue mentioned above, Db2 will be
  enhanced to prefetch all pages invalidated that exists in
  the buffer pools to avoid sync I/Os (aka. refresh prefetch)
  after cross invalidation. Today, setting VPSEQT(100) will
  trigger prefetch and avoid sync read for the buffer pool with
  PGSTEAL(NONE). This behavior will not be changed by this
  APAR.
  
  Besides the refresh prefetch solution, Db2 will also
  introduce the capability to specify the pseudo close interval
  for a specific buffer pool, which is the interval that a
  partition or page-set remains read-write in a specific
  buffer pool after being updated. This interval is currently
  controlled for all buffer pools by the PCLOSET subsystem
  parameter value.
  
  
  A new option REFPF will be added for the Db2 command ALTER
  BUFFERPOOL.
  
  REFPF
  Specifies whether to refresh the cross invalidated pages via
  prefetch.
  
  (NO)
       Specifies that the pages will not be refreshed after
       cross invalidation.
       This value is the default.
  
  (YES)
       Specifies that the pages will be refreshed after cross
       invalidation.
  
  The DSNB406I message will updated to add the REFPF attribute.
  
  A new message DSNB554I will be added to indicate that the
  requested change to the REFPF attribute has been accepted
  and took effect.
  
  Two new counters QW0201OR, QW0201NR will be added into
  IFCID 0201 for the refresh prefetch (REFPF) attribute.
  QW0201OR - WHETHER A PAGE IS REFRESHED AFTER CROSS
             INVALIDATION ('Y' OR 'N').
  QW0201NR - REFPF ATTRIBUTE AFTER THE ALTER BUFFERPOOL
             COMMAND WAS ISSUED ('Y' OR 'N').
  
  A new statistics counter QBSTSRF will be added into
  the IFCID 0002 trace records.
  QBSTSRF  - TOTAL NUMBER OF PAGES REFRESHED SYNCHRONOUSLY.
  
  A new message DSNB417I will be added to display the new
  counter QBSTSRF for the buffer pool when the DETAIL option is
  specified.
  
  
  The ALTER BUFFERPOOL command is enhanced to accept a new
  option VPCLOSET, which specifies the interval that a
  partition or page-set remains read-write in a specific
  buffer pool after being updated. This setting overrides the
  PCLOSET subsystem parameter setting for the specified
  buffer pool.
  
  VPCLOSET (integer )
  Changes the pseudo-close interval for the buffer pool. The
  value of integer specifies the number of minutes that a
  partition or page set remains read-write after it is last
  updated. After the specified number of minutes, Db2 converts
  the set or partition to read-only.
  
  The value of integer must be 0-32767, inclusive. The initial
  default value is 0.
  
  If VPCLOSET(0) is specified, the PCLOSET subsystem parameter
  value specifies the pseudo-close interval for the buffer
  pool.
  
  The DSNB404I message will updated to add the VPCLOSET
  attribute.
  
  A new message DSNB509I will be added to indicate that an
  attempt was made to change a buffer pool's VPCLOSET attribute
  to an invalid value using the ALTER BUFFERPOOL command.
  
  A new message DSNB518I will be added to indicate that an
  ALTER BUFFERPOOL command specified a VPCLOSET equal to the
  current buffer-pool-level pseudo-close interval of the buffer
  pool.
  
  A new message DSNB528I will be added to indicate the
  successful modification of the buffer-pool-level pseudo-close
  interval of the buffer pool.
  

APAR Information

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

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

  UO02763

Modules/Macros

• DSN9SCNA DSNB1ABP DSNB1BVP DSNB1CMD DSNB1CNE DSNB1CPF DSNB1CPL
  DSNB1DBP DSNB1DRN DSNB1DVP DSNB1GET DSNB1GFP DSNB1GRA DSNB1LTS
  DSNB1LTX DSNB1PCP DSNB1PLK DSNB1PPP DSNB1RFR DSNB1SPF DSNB1SWD
  DSNB1SWS DSNB1TSD DSNB5DEL DSNB5RAP DSNDQBST DSNDQW03 DSNFBDIR
  DSNFCDIR DSNIIEPL
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RD10 PSY UO02763

     UP25/04/18 P F504  

Fix is available

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