4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 01211: Device I/O Queue Time Exceeds Max

01211: Device I/O Queue Time Exceeds Max

FILE: Device Activity File
SAS FILE NAME: DAYS.HARDVA01
SOURCE LOCATION: prefix.MICS.USER.SOURCE(DYRMFEXC)

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

PURPOSE:  Identify potential I/O bottlenecks resulting from
excessive device I/O queue time.

RATIONALE:  An estimate of the average delay time, per
successful I/O, identifies devices for which both the number
of delayed I/Os is high and the duration of each delay is
significant.  Because it is an estimate rather than a time
measure, it is susceptible to statistical bias and should not
be calculated when the number of successful I/Os is too low.

DEFINITION:  The exception is detected when the average delay
time per I/O exceeds the installation-defined maximum and the
number of I/Os per hour also exceeds an installation-defined
minimum.

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:

** 01211 DEVICE I/O QUEUE TIME EXCEEDS MAX;
IF DVASSC GT 1000 THEN Q_TIME=DVAAVIOS;
ELSE IF DVASIO GT 1000
 THEN Q_TIME=(DVAAVQUE*DURATION)/DVASIO;
IF Q_TIME GT queue-time THEN DO;
    EXCCODE='01211'; SEVERITY='I'; MGMTAREA='PERFORMANCE';
    EXCDESC1='DEVICE I/O QUEUE TIME EXCEEDS MAX';
    EXCDESC2='Q TIME (SS.TTT)=' !! PUT(Q_TIME,6.3) !!
                       ', VOL=' !! VOLSER          !!
                      ', ADDR=' !! PUT(DEVNUM,HEX4.) !!
                      ', TYPE=' !! DEVTYPE;
    LINK HIT;
END;

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

queue-time - The maximum I/O time in seconds is specified.  A
.030 second threshold would appear as:

Q_TIME GT .030