IBM Support

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

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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 number

    IT29631

  • Reported component name

    INFORMIX SERVER

  • Reported component ID

    5725A3900

  • Reported release

    C10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-07-05

  • Closed date

    2020-12-09

  • Last modified date

    2020-12-09

  • 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

[{"Line of Business":{"code":"LOB10","label":"Data and AI"},"Business Unit":{"code":"BU029","label":"Software"},"Product":{"code":"SSGU8G","label":"Informix Servers"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"C10"}]

Document Information

Modified date:
10 December 2020