CA IDMS IUA EIUA

Re:Re: OLQ Select index set

  • 1.  Re:Re: OLQ Select index set

    Posted 08-20-2010 12:12 PM
    If you have up to date statistics for your network DBs (UPDATE
    STATISTICS FOR SCHEMA schema) and IDMS considers that the fastest way to
    get that record or records is to go through S-999-783 to get it, then it
    will. If IDMS considers that an area sweep will be faster then it will
    do that.

    Your statement in SQL is simply

    SELECT * FROM FSPR-VAFVAST WHERE VAF-RNR = 210002735

    You can fool IDMS if you think it is taking the wrong decision using the
    OPTIMIZE FOR n ROWS clause. If you say OPTIMIZE FOR 1 ROWS then it will
    almost certainly go for the index. If you say OPTIMIZE FOR 999999 ROWS
    then it will probably go for the Area sweep.

    You could also do an Explain on the SQL to see what IDMS is actually
    going to do. The example to do it is in the DISTSRC library.

    BROWSE CAI.GJR170.DISTSRC(EXPLDDL) Line 00000000 Col
    001 080 .
    Command ===> Scroll
    ===> CSR .
    ********************************* Top of Data
    ********************************** .
    ------------------------------------------------------------------------
    .
    --CONTAINS PTF#r17 Support full outer join sort/merge  DEFJE01 06/08/21-
    .
    --CONTAINS PTF#IDMS/3170                               PERCA02 05/16/05-
    .
    --CONTAINS PTF#IDMS/3096                               RHORI01 12/10/04-
    .
    -- -
    .
    -- The following SQL definitions can be very helpful when using the -
    .
    -- EXPLAIN command. -
    .