4. EXCEPTIONS › 4.3 Detailed Exception Descriptions › 01212: Device I/O Service Time Exceeds Max

01212: Device I/O Service 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 device I/O bottlenecks resulting
from excessive I/O service time.

RATIONALE:  An estimate of the average service time per I/O
is useful in identifying devices that spend significant time
transferring data or significant seek-and-search times.  The
identified devices may then be analyzed for data set
placement, appropriate blocking, and so on.  This condition
can also result from heavy use of a device by an access
method (or user written EXCP technique) that does not use or
support RPS.

DEFINITION:  This exception is detected when the average I/O
service time to a device exceeds the installation-defined
maximum.

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:

** 01212 DEVICE I/O SERVICE TIME EXCEEDS MAX;
*;
IF DVASSC GT io-rate THEN S_TIME=DVAAVSER;
IF S_TIME GT service-time
 THEN DO;
  EXCCODE='01212'; SEVERITY='I'; MGMTAREA='PERFORMANCE';
  EXCDESC1='DEVICE I/O SERVICE TIME EXCEEDS MAX';
  EXCDESC2='SERV TIME (SS.TTT)=' !! PUT(S_TIME,6.3)  !!
                        ', VOL=' !! VOLSER           !!
                       ', ADDR=' !! PUT(DEVNUM,HEX4.)!!
                       ', TYPE=' !! DEVTYPE;
  LINK HIT;
END;

THRESHOLD MODIFICATION:  The user should modify the io-rate
and service-time values according to the following
conventions:
io-rate - The minimum number of I/O operations is specified.
A threshold of 1000 I/Os would appear as:

DVASSC GT 1000

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

S_TIME GT .030