4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 06015: MFS Prefetch I/O Rate Exceeds Standard

06015: MFS Prefetch I/O Rate Exceeds Standard

    FILE:            IMS System Activity
    SAS FILE NAME:   DETAIL.IMSISY01
    SOURCE LOCATION: sharedprefix.MICS.SOURCE(DYIMSEXC)

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

    PURPOSE:  Identifies the time period during which the
message MFS pool was over-committed.

    RATIONALE:  An abnormally high MFS prefetch I/O rate may
indicate misuse of MFS.  Proliferation of formats with no
attempt to use common displays, may lead to high I/O here.
Prefetch I/O is generally preferable to immediate fetch I/O
providing the prefetch is satisfied before a subsequent
immediate fetch request.  If a significant portion of the
immediate fetch I/O is satisfied from the prefetch queue,
prefetch may be considered for elimination from the system.
Prefetch is determined by the 'NEXT=' parameter in the MFS
gen.  Take care to use this parameter only where reasonable.

    DEFINITION:   This exception is detected when the MFS
buffer prefetch I/O rate exceeds the installation-defined
limit.  It does not apply to IMS 4.1 and higher systems.

    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:

*
**  06015
**  MFS PRE FETCH I/O RATE EXCEEDS STANDARD
*;
IF (ISYFMPFI/DURATION) > prefetch-I/O-rate
 THEN DO;
  X = ISYFMPFI / DURATION;
  EXCCODE='06015'; SEVERITY='W'; MGMTAREA='PERFORMANCE';
  EXCDESC1=
  'MFS PRE FETCH I/O RATE EXCEEDS STANDARD';
  EXCDESC2='MFS PRE FETCH I/O RATE ='
           || PUT(X,7.2) ||
           ' if from PRE FETCH =' ||
           PUT(ISYPCIPQ,6.2) || '%';
  LINK HIT;
END;

    THRESHOLD MODIFICATION:  Modify the value used for the
MFS prefetch-I/O-rate.