PM74406: ECSA STORAGE DEPLETED BY MANY SSRB AND LSSD FROM DIST ADDRESS SPACE AND THE LPAR WAS PLACED IN WAIT STATE DB2STGLK/K

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DB2DDF DB2INACTIVE defects pm74406 dpm74406
  MVS system was placed in a wait01C-008 state due to ECSA
  storage exhausted.  Scrutiny of the ECSA storage shows many
  SSRB and LSSD issued out of DB2 DIST address space within
  the last 2 minutes right before the MVS crash.
  The DB2 stack storage was extremely high at 1.4G. The stack
  storage are from thousands of EBs with calling chains DSNLAGNT
  to DSNVDBPM. The VLCASAGT latch wait chain has over 21,000 of
  waiters.  DDF zparm POOLINAC is zero when this occurred.
  ************************************************************
  Additional Symptoms and keywords:
    DSNTIP5 POOL THREAD TIMEOUT 0
    DSN6FAC POOLINAC 0
    Loop Looping LP Hang Hung Wait Wt
    Short on Storage SOS
    DB2TERM
    DB2STGLK/K
  

Local fix

• A temporary bypass is to set zparm POOLINAC to a non-zero value
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Distributed Data Facility (DDF) users.   *
  *                 Specifically those where DB2 is configured   *
  *                 with (DSNTIPR) DDF THREADS INACTIVE          *
  *                 (DSN6FAC CMTSTAT=INACTIVE) and (DSNTIP5)     *
  *                 POOL THREAD TIMEOUT 0 (DSN6FAC POOLINAC=0).  *
  *                 DB2 10 for z/OS users only.                  *
  ****************************************************************
  * PROBLEM DESCRIPTION: Massive accumulation of DB2 DDF server  *
  *                      threads, DBATs, in termination          *
  *                      processing. The excessive number of     *
  *                      DBATs causes a very high utilization    *
  *                      of ssnmDIST private (autodata/stack)    *
  *                      storage, (above the line) ECSA, and     *
  *                      potentially (below the line) CSA. The   *
  *                      excessive ECSA and CSA utilization may  *
  *                      impact the entire z/OS host, even to    *
  *                      the point of requiring an IPL.          *
  *                      The problem only occurs if DB2 is       *
  *                      configured with DSN6FAC POOLINAC=0.     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  New function provided in DB2 10 for z/OS may lead to a
  condition where DDF server threads (DBATs) can be created
  and then immediately terminated. Each terminating DBAT will
  schedule the creation of a replacement DBAT which in turn
  immediately terminates. This process continues and results in
  an accumulation of DBATs. The accumulation of DBATs causes a
  high utilization of sssnDIST private storage and may also
  cause a high utilization of ECSA and, potentially, CSA
  storage. The high utilization of ECSA and CSA may ultimately
  impact all activity on the z/OS host which may require an IPL.
  The condition only occurs in  DB2 10 for z/OS and only if
  "DDF Threads" Inactive (DSN6FAC CMTSTAT=INACTIVE) is specified
  in conjunction with a "Pool Thread Timeout" (DSN6FAC POOLINAC)
  value of zero.
  

Problem conclusion

• DB2 DDF Inactive Thread support processing, operating in a
  POOLINAC=0 environment, has been changed to recognize a
  replacement DBAT and allow the newly created DBAT to be
  suspended (rather than allowing it be immediately terminated).
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UK83176

Modules/Macros

• DSNLQDIS
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK83176

     UP12/11/21 P F211

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.