IC87559: SRV_FET_BUF_SIZE ENVIRONMENT VARIABLE DOCUMENTATION IS INACCURATE

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APAR status

  • Closed as documentation error.

Error description

  • Since 11.70.xC5 release of IBM Informix Server the
    SRV_FET_BUF_SIZE variable is documented in 'Guide to  SQL:
    Reference' book and it's also mentioned in  'JDBC Driver Guide'.
    
    Unfortunately, the documentation in SQL Reference is incomplete
    in 3 statements:
    
    1) where it should be set
    "Use the SRV_FET_BUF_SIZE environment variable to specify the
    size of the fetch buffer used for distributed transactions
    between database servers."
    
    With the current implementation the variable setting takes
    effect only when it is set in engine starting environment.
    
    2) the upper limit for the variable:
    "size is a positive integer that is no greater than 1048576 (1
    MB), specifying the size (in bytes) of the fetch buffer that
    holds data retrieved by a distributed transaction query.
    ...
    No error is raised if SRV_FET_BUF_SIZE is set to a value that is
    less than the default size or that is greater than 1048576
    (1MB). If SRV_FET_BUF_SIZE is set to a value greater than
    1048576 then the value is set to 1048576."
    
    This is true for 11.70.xC5 and newer versions. In older 11.70
    releases (up to and including 11.70.xC4) the upper limit is
    32767.
    
    3) its scope
    "A valid SRV_FET_BUF_SIZE setting is in effect for the local
    database server and for any remote database server from which
    you retrieve rows through a distributed query in which the local
    server is the coordinator and the remote database is
    subordinate."
    
    In fact this variable applies to distributed (cross-server)
    queries only (it doesn't affect the size of the fetch buffer for
    the 'client to local server' communication).
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * Users of 11.70xC7 and earlier versions.                      *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description (SRV_FET_BUF_SIZE environment variable *
    * documentation is inaccurate)                                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * See information in the problem conclusion section.           *
    ****************************************************************
    

Problem conclusion

  • The following information is applicable only for version
    11.70.xC5 and newer versions:
    
    The SRV_FET_BUF_SIZE environment variable defines the fetch
    buffer size only for cross-server distributed DML operations,
    and only on the local database server.  For all participating
    servers to use fetch buffers of up to one MiB, SRV_FET_BUF_SIZE
    must also be set in the starting environment of each remote
    server.  That setting has no effect on local or cross-database
    queries, whose buffer size FET_BUF_SIZE defines.
    
    The following information is applicable only for version
    11.70.xC4 and older versions:
    
    The SRV_FET_BUF_SIZE environment variable defines the fetch
    buffer size only for cross-server distributed DML operations,
    and only on the local database server.  For all participating
    servers to use fetch buffers of up to 32767 bytes,
    SRV_FET_BUF_SIZE must also be set in the starting environment of
    each remote server.  That setting has no effect on local or
    cross-database queries, whose buffer size FET_BUF_SIZE defines.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC87559

  • Reported component name

    INFORMIX SERVER

  • Reported component ID

    5725A3900

  • Reported release

    B70

  • Status

    CLOSED DOC

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-10-26

  • Closed date

    2014-02-26

  • Last modified date

    2014-02-26

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

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

Fix information

Applicable component levels



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Document information


More support for:

Informix Servers

Software version:

B70

Reference #:

IC87559

Modified date:

2014-02-26

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