MODIFY IOPURGE command


>>-MODIFY-- --procname--,--IOPURGE--=--timeout_value-----------><

Abbreviations

Operand	Abbreviation
MODIFY	F

Purpose

Using the MODIFY IOPURGE (input/output purge) command, you can set a time interval after which outstanding I/O is assumed to be lost and recovery steps are taken. The types of outstanding I/O that are examined are CDINIT requests, direct search list requests, APPN search requests, and HPR route setup requests.

Before the availability of this function (or when IOPURGE is set to zero), outstanding session requests could remain indefinitely. For example, when an intermediate host that is used in session routing goes down, no response is received to a session establishment request and the LU remains hung indefinitely. By setting an IOPURGE value, you can, in effect, cancel session requests that fail to complete in a certain amount of time. This frees the LU so you can request a session using an alternate path.

It is recommended that you set an IOPURGE value of 3 minutes or more. In some circumstances, for example logging on a remote LU through a slow modem, session setup might take longer and the IOPURGE should be adjusted upward accordingly. A good rule of thumb is to set the IOPURGE value for twice as long as session setup takes. If you set IOPURGE too low, the session request is canceled before a response can be received, and you will have to repeat the session request.

Note: You can use the MODIFY VTAMOPTS command to perform the same function as this command.

Operands

procname

The procedure name for the command. If procname in the START command was specified as startname.ident, where startname is the VTAM® start procedure and ident is the optional identifier, either startname.ident or ident can be specified for procname.

If procname in the START command was startname, startname must be specified for procname.

IOPURGE=timeout_value

Specifies the time interval allowed to elapse before outstanding I/O is assumed to be lost. When this time interval expires, recovery steps are taken. VTAM supports this feature for CDINIT requests, direct search list requests, APPN search requests, and HPR route setup requests.

The time interval can be specified in seconds, minutes, hours, or days. The minimum value is 30 seconds. The maximum value is 7 days, or the equivalent value in seconds, minutes, or hours. A value of 0 deactivates the IOPURGE function. If you code a value from 1 to 30, VTAM sets IOPURGE to 30 seconds.

Note: To reduce potential performance strain, set IOPURGE greater than 2 minutes.

IOPURGE=n or IOPURGE=nS: Specifies the number of seconds that can pass before a response is assumed to be lost. By default, the time is assumed to be seconds, unless M, H, or D is specified.
IOPURGE=nM: Specifies the number of minutes that can pass before a response is assumed to be lost.
IOPURGE=nH: Specifies the number of hours that can pass before a response is assumed to be lost.
IOPURGE=nD: Specifies the number of days that can pass before a response is assumed to be lost.