4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 09012: VTOC Reorganization Recommended

09012: VTOC Reorganization Recommended

    FILE:             VOA Volume Allocation File
    SAS FILE NAME:    DETAIL.VCAVOA01
    SOURCE LOCATION:  prefix.MICS.USER.SOURCE(DYVCAEXC)

    SEVERITY:         Warning       (SEVERITY='W')
    MANAGEMENT AREA:  Performance   (MGMTAREA='PERFORMANCE')

    PURPOSE:  Identifies when a VTOC's DSCBs are not
localized at the front of the VTOC.

    RATIONALE:  VTOC search lengths are dependent on a DSCB
Format 1 "highwater mark" that is maintained in the Format 4
DSCB.  If the used DSCBs have become spread out within the
VTOC, the search lengths can increase significantly, which
results in poor performance.  This spreading effect becomes
a problem only when a large amount of VTOC space is in use.

    DEFINITION:  This exception is based on the number of
DSCBs that the Collector scanned to read all of the used
DSCBs.  This value divided by the number of used DSCBs is
a good indication of how spread out the used DSCBs are.  A
further check is made to see what percent of VTOC DSCBs are
in use.

    EXCEPTION STATEMENTS:  The SAS statements identifying the
exception situation and describing the condition are stored
in the source member named in SOURCE LOCATION and are
described below:

/*---------------------------------------------------------*/
/*                                                         */
/*  09012                                                  */
/*  VTOC REORGANIZATION RECOMMENDED                        */
/*                                                         */
/*---------------------------------------------------------*/
IF DSCBU AND VOAINDXD NE 'Y' THEN DO;
  SPREAD=VOADSCBR/DSCBU;
  PCVTU =DSCBU/VOADSCBS;
  IF SPREAD GE #spread PCVTU GE #pcvtu
   THEN DO;
    EXCCODE='09012'; SEVERITY='W'; MGMTAREA='PERFORMANCE';
    EXCDESC1='VTOC REORGANIZATION RECOMMENDED';
    EXCDESC2='VTOC SPREAD INDEX=' || PUT(SPREAD,3.1) ||
             ', VOL=' || VOLSER;
    LINK HIT;
  END;
END;

    THRESHOLD MODIFICATION:  The user should modify the
#spread and #pcvtu values according to the following
conventions:

    #spread - The maximum acceptable spread index value for
         DSCBs within the VTOC.  A value of 2 means that the
         usable VTOC is twice as large as it needs to be
         (i.e., every other DSCB is a free DSCB).  A value of
         2 would be specified as:

         IF SPREAD GE 2

    #pcvtu  - The minimum percent of the VTOC in use.  Spread
         indices will not be checked for VTOCs whose percent
         of space used is below this value.  The value is the
         percent of VTOC DSCBs that are in use.  A value of
         25 percent would be specified as:

         IF PCVTU GE 25