4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 01200: Device Avg Queue Length Exceeds Max

01200: Device Avg Queue Length Exceeds Max

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

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

PURPOSE:  A high average queue length for a device may
indicate devices that are I/O bottlenecks.

RATIONALE:  The average size of the queue for an individual
device reflects the number of times I/O was queued for that
device.  This may identify devices that cause I/O delay.  If
the I/O to the device is all from one subsystem, which
schedules its own I/O, this indicator will show no queue
length, and thus is useful primarily on devices used by
multiple address spaces.

DEFINITION:  This exception is detected when the average
queue length for a device exceeds the installation-defined
maximum.  Different thresholds should be established for
different device classes and types.

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:

** 01200 DEVICE AVG QUEUE LENGTH EXCEEDS MAX;
*;
IF DVAAVQUE GT queue
 THEN DO;
  EXCCODE='01200'; SEVERITY='W'; MGMTAREA='PERFORMANCE';
  EXCDESC1='DEVICE AVG QUEUE LENGTH EXCEEDS MAX';
  EXCDESC2='AVG Q=' !! PUT(DVAAVQUE,5.2) !!
           ', VOL=' !! VOLSER            !!
          ', ADDR=' !! PUT(DEVNUM,HEX4.) !!
          ', TYPE=' !! DEVTYPE;
  LINK HIT;
END;

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

queue - The average queue length is specified.  A threshold
queue length of 0.1 appear as:

DVAAVQUE GT .1