4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 01100: Selector Channel Overloaded

01100: Selector Channel Overloaded

    FILE: Physical Channel Activity File
    SAS FILE NAME: DAYS.HARPCA01
    SOURCE LOCATION: prefix.MICS.USER.SOURCE(DYRMFEXC)

    SEVERITY: Impacting            (SEVERITY='I')
    MANAGEMENT AREA: Performance   (MGMTAREA='PERFORMANCE')

    PURPOSE:  Identify overloaded selector channels which may
be a symptom of I/O problems and performance degradation.

    RATIONALE:  As physical channel busy increases, the
probability of I/O delay increases exponentially.  It can be
inferred that I/O delay due to channel busy is occurring from
a high channel busy situation.  This problem may be
particularly impacting if a critical data set such as the IMS
log tape is on a device which must be accessed through this
channel.

    DEFINITION:  This exception is detected when the channel
busy percentage exceeds the installation defined maximum.  A
selector channel is overloaded when its channel busy percent
exceeds 60-70%, assuming few, if any, DASD devices.

    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:

** 01100 SELECTOR CHANNEL OVERLOADED;
IF CHANTYPE='SELECTOR'
 AND PCAPCBSY > percent
 THEN DO;
  EXCCODE='01100'; SEVERITY='I'; MGMTAREA='PERFORMANCE';
  EXCDESC1='SELECTOR CHANNEL OVERLOADED';
  EXCDESC2='BUSY=' || PUT(PCAPCBSY,5.1) ||
        '%, CHAN=' || CHANNEL;
  IF RMFVER<='08 '
    THEN EXCDESC2=TRIM(EXCDESC2) || ', SET=' || CPUID;
  LINK HIT;
END;

    THRESHOLD MODIFICATION:  The user should modify the
percent value according to the following convention:

    percent - The maximum percent channel busy is specified.
A 60 percent threshold would appear as:

    PCAPCBSY > 60