IT29631: BATCHEDREAD_INDEX=1, NON-LOGGED DATABASE, AND REVERSE INDEX SCAN, INDEX CORRUPTION CAN MAKE A SQLEXEC THREAD RUN IN A TIGHT LOOP

APAR status

• Closed as program error.

Error description

• When BATCHEDREAD_INDEX is turned on (so set to 1) and a query
  using a reverse index scan on table in a non-logged database, if
  an index is corrupted in such a way so that the key value exists
  in the index, bu the rowid for the data page has been deleted,
  the sqlexec will hang and get stuck in a tight loop and tie up a
  cpu vp.
  
  The stack would look something like this:
  
  phposition()
  rsread()
  fmread()
  getsinglerow()
  readidx_new()
  gettupl()
  scan_next()
  getrow()
  fetchrow()
  exfetch()
  sql_nfetch()
  sq_nfetch()
  sqmain()
  spawn_thread()
  th_init_initgls()
  startup()
  
  The looping involves readidx_new() and all the functions below
  so the thread never gets out of readidx_new() and it ends up
  continuously trying to read the same row over and over again,
  never looping and never completing.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of Informix Server prior to 12.10.xC15 and 14.10.xC4.  *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Informix Server 12.10.xC15 (when available) or    *
  * 14.10.xC4.                                                   *
  ****************************************************************
  

Problem conclusion

• Fixed in Informix Server 12.10.xC15 and 14.10.xC4.
  

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