IT34433: DRDA CLIENTS MAY SEE AN EXCEPTION IN DRDA_RECEIVE_BUFF IN A LOW/OUT OF MEMORY SITUATION

APAR status

• Closed as program error.

Error description

• Imagine we have an environment with DRDA clients using a
  DRDA_COMMBUFFSIZE setting of 2048.
  The instance is restricted to 16GB by edition limits. After a
  certain time the memory turns to be
  fragmented in the way that the largest amount of continuous
  blocks is lower then 512 Blocks needed
  for the communication in DRDA even there are plenty buffers
  available:
  
  id         key        addr             size             ovhd
  class blkused  blkfree
  9404417    52564802   4cc00000         14763950080
  173016984 V*    128061   3476419
  9568263    52564807   441e00000        35651584         419352
  V*    135      8569
  
  onstat -g nbm |  grep larg
   used = 128061, largest_free = 511
   used = 135, largest_free = 511
  
  In this case frequent af files are seen with
  
  0x0000000000bb411e (/opt/IBM/informix/bin/oninit)
  _Z17drda_receive_buff
  0x0000000000bb4367 (/opt/IBM/informix/bin/oninit)
  _Z15sqljcIntReceiveP10sqljCmnMgr
  0x0000000000bac101 (/opt/IBM/informix/bin/oninit)
  _Z14sqljcReadHdrAsP10sqljCmnMgrPt
  0x0000000000ba062f (/opt/IBM/informix/bin/oninit) sqljsParse
  0x0000000000b984c6 (/opt/IBM/informix/bin/oninit) do_drdamain
  0x0000000000ae472a (/opt/IBM/informix/bin/oninit) drdamain
  0x000000000154208b (/opt/IBM/informix/bin/oninit) spawn_thread
  0x0000000001401c70 (/opt/IBM/informix/bin/oninit)
  th_init_initgls
  0x0000000001448997 (/opt/IBM/informix/bin/oninit) startup
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of Informix Server prior to 12.10.xC15 and 14.10.xC6.  *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * You have an environment with DRDA clients using a            *
  * DRDA_COMMBUFFSIZE setting of 2048.                           *
  * The instance is restricted to 16GB by edition limits. After  *
  * a certain time the memory turns to be                        *
  * fragmented in the way that the largest amount of continuous  *
  * blocks is lower then 512 Blocks needed                       *
  * for the communication in DRDA even though there are plenty   *
  * of buffers available:                                        *
  *                                                              *
  * id         key        addr             size             ovhd *
  * class blkused  blkfree                                       *
  * 9404417    52564802   4cc00000         14763950080           *
  * 173016984 V*    128061   3476419                             *
  * 9568263    52564807   441e00000        35651584              *
  * 419352                                                       *
  * V*    135      8569                                          *
  *                                                              *
  * onstat -g nbm |  grep larg                                   *
  *  used = 128061, largest_free = 511                           *
  *  used = 135, largest_free = 511                              *
  *                                                              *
  * In this case frequent assert failure files are seen with the *
  * following stack:                                             *
  *                                                              *
  * (/opt/IBM/informix/bin/oninit) _Z17drda_receive_buff         *
  * (/opt/IBM/informix/bin/oninit)                               *
  * _Z15sqljcIntReceiveP10sqljCmnMgr                             *
  * (/opt/IBM/informix/bin/oninit)                               *
  * _Z14sqljcReadHdrAsP10sqljCmnMgrPt                            *
  * (/opt/IBM/informix/bin/oninit) sqljsParse                    *
  * (/opt/IBM/informix/bin/oninit) do_drdamain                   *
  * (/opt/IBM/informix/bin/oninit) drdamain                      *
  * (/opt/IBM/informix/bin/oninit) spawn_thread                  *
  * (/opt/IBM/informix/bin/oninit) th_init_initgls               *
  * (/opt/IBM/informix/bin/oninit) startup                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Informix Server 12.10.xC15 (when available) or    *
  * 14.10.xC6 (when available).                                  *
  ****************************************************************
  

Problem conclusion

• Fixed in Informix Server 12.10.xC15 and 14.10.xC6.
  

Temporary fix

Comments

APAR Information

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

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

Fix information

• Fixed component name

  INFORMIX SERVER

• Fixed component ID

  5725A3900

Applicable component levels