4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 00315: "Quiet Mode" Entered Due to Machine Checks

00315: "Quiet Mode" Entered Due to Machine Checks

FILE              TSO System Activity
SAS FILE NAME     DETAIL.TSOTSO01
SOURCE LOCATION   sharedprefix.MICS.SOURCE(DYTSOEXC)

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

PURPOSE      Indicates that numerous recoverable machine
             failures have occurred.

RATIONALE    "Soft" machine checks may require recovery
             processing which degrades the effective speed of
             the machine.

             Modern computing hardware has a significant
             ability to recover from internal hardware
             problems without any effect on the logical
             operation of the system (but possibly with some
             performance degradation).  For example, the
             system can usually recover from a single-bit
             error in any location of main memory.
             Furthermore, if the hardware cannot recover from
             the error, it is possible that the software can
             (for example by ABENDing just the task which
             took the hit).

             Even though the system has recovered from an
             error, the hardware signals to MVS that an error
             occurred so that a record of it can be made for
             tracking and analysis purposes.  The signal is
             called a "soft" machine check.

             "Soft" machine checks are named this because
             they do not prevent the machine from processing
             correctly.  MVS can mask them to prevent the
             logging of gross amounts of redundant data.  MVS
             does this when it receives a certain number of
             machine checks of a given type.  When a subclass
             of soft machine failure is masked, MVS is said
             to be in "quiet mode" for that class of failure.
             While in quiet mode, no console messages or
             LOGREC records will be written for that kind of
             machine error.  When MVS goes into "quiet mode,"
             it issues a message to that effect to the master
             console.

             An MVS Operator command can be issued to take
             the system out of a quiet mode after the failing
             component has been repaired.

DEFINITION   This exception is noted when any of the
             following data elements are found with a nonzero
             value:

             TSOXSMQY - Intvls When Sys Recover Check Msgs
                        Quiet

             See Appendix B for more information on this
             data element.

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

************************************************************;
*
** 00315
** 'QUIET MODE' ENTERED DUE TO MACHINE CHECK
*;
IF TSOXSMQY > 0
 THEN DO;
  EXCCODE='00315'; SEVERITY='W'; MGMTAREA='PERFORMANCE';
  EXCDESC1='QUIET MODE ENTERED DUE TO MACHINE CHECK';
       EXCDESC2=' SYSTEM RECOVERY CHECK'
            || ' ENDTS=' || PUT(ENDTS,DATETIME19.2);
  LINK HIT;
END;

THRESHOLD    None required.
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