MODIFY BFRUSE command


                                      .-,--BUFFER--=--IOBUF----.                         
>>-MODIFY-- --procname--,--BFRUSE--,--+------------------------+--,--XPANLIM--=--value-><
                                      '-,--BUFFER--=--+-IO00-+-'                         
                                                      '-IO---'

Abbreviations

Operand	Abbreviation
MODIFY	F
BUFFER	BUF

Purpose

Using the MODIFY BFRUSE command, you can dynamically change the total amount of common service area (CSA) storage that VTAM® is allowed to use for the IO buffer pool. See z/OS Communications Server: SNA Resource Definition Reference for information about the xpanlim parameter of IOBUF buffer pool start option.

Note:

This command can be used to increase the IO buffer pool expansion limit by selecting a value greater than the current total storage used for the IO buffer pool. It can also be used to set the value to 0, which removes the expansion limit. This means that the IO buffer pool has no expansion limit. It will be set to the current CSALIMIT value.
This command fails if a value of 0 is coded for the xpanno parameter for the IOBUF operand at VTAM startup (indicating static buffering specified).
If the XPANLIM value is less than the current allocated total IO buffer pool storage, the expansion limit will be set to the current allocated IO buffer pool storage.
If the XPANLIM value is greater than the current CSALIMIT value, the expansion limit will be set to the current CSALIMIT value.

Operands

procname

The procedure name for the command. If procname in the START command is 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.

BFRUSE

Specifies that the command is to modify a VTAM buffer pool value.

BUFFER=IOBUF | IO00 | IO: This parameter is optional, as the XPANLIM parameter applies only to the IOBUF pool.

XPANLIM=value

Specifies the new total size for the IO buffer pool including the base allocation and expansions.

Value can be specified in any of the following forms:

n or nk: The number of 1024-byte increments to be used. The value of n is rounded up to the next multiple of 4.
qM: The number of 1 MB increments that are to be used.

Though the range for value is 0 - 2097152 KB, the valid range is between the current pool allocation and the VTAM CSALIMIT value. If a value is specified less than that currently in use (except 0), the current in-use value will become the expansion limit. If a value is specified greater than the current VTAM CSA limit, the expansion limit will be set to the VTAM CSA limit.

A value of 0 is also valid and is used to remove the IO buffer pool expansion limit.

See DISPLAY BFRUSE command for information about how to use that command to determine the current CSALIMT value and the current IOBUF storage usage.

The current VTAM CSALIMIT setting is contained in message IST449I.

The current total IO buffer pool allocation is obtained by multiplying the Max Total value from message IST923I by the BUFSIZE value in message IST920I. This is an approximate value, as the IO buffer size selected may result in unused space in a 4K page. This unused space is added to the total space calculation for expansion limit.

You can also determine whether dynamic buffering is in effect for the IOBUF pool by checking to see whether the EXP INCREMENT field in message IST920I contains a numeric value. (A value of *NA* indicates that xpanno=0 was coded on the IOBUF start option at VTAM startup, and that static buffering is to be used.)

Examples

Modify vtam,bfruse,buf=iobuf,xpanlim=2400K
IST097I   MODIFY ACCEPTED
IST495I   XPANLIM HAS BEEN SET TO 2400K
IST223I   MODIFY BFRUSE COMMAND COMPLETED
IST314I   END