SET LOG (change log system settings) on z/OS

On z/OS®, use the MQSC command SET LOG to dynamically change certain log system parameter values that were initially set by your system parameter module at queue manager startup.

Using MQSC commands

For information on how you use MQSC commands, see Performing local administration tasks using MQSC commands.

You can issue this command from sources 12CR. For an explanation of the source symbols, see Sources from which you can issue MQSC commands on z/OS.

Syntax diagram
Usage notes for SET LOG
Parameter descriptions for SET LOG
Parameter block

Synonym: SET LOG

SET LOG

Parameter Block

Notes:

¹ Valid only when the queue manager is a member of a queue sharing group.

Usage notes for SET LOG

Any changes to WRTHRSH take immediate effect.
Any change to MAXARCH takes effect for the next scheduled offload (that is, not for any offload in progress at the time the command is issued).

Parameter descriptions for SET LOG

CMDSCOPE

This parameter applies to z/OS only and specifies how the command runs when the queue manager is a member of a queue sharing group.

'': The command runs on the queue manager on which it was entered. This is the default value.
qmgr-name: The command runs on the queue manager you specify, providing the queue manager is active within the queue sharing group.
You can specify a queue manager name, other than the queue manager on which it was entered, only if you are using a queue sharing group environment and if the command server is enabled.You cannot use CMDSCOPE( qmgr-name) for commands issued from the first initialization input data set, CSQINP1.
*: The command runs on the local queue manager and is also passed to every active queue manager in the queue sharing group. The effect of this is the same as entering the command on every queue manager in the queue sharing group.
You cannot use CMDSCOPE(*) for commands issued from CSQINP1.

DEFAULT

Reset all the log system parameters to the values specified at queue manager startup.

Parameter block

[z/OS] For a full description of these parameters, see Using CSQ6LOGP.

Parameter block is any one or more of the following parameters that you want to change:

COMPLOG

This parameter specifies whether compression is used by the queue manager when writing log records. Any compressed records are automatically decompressed irrespective of the current COMPLOG setting.

The possible values are:

ANY: Enable the queue manager to select the compression algorithm that gives the greatest degree of log record compression. Using this option currently results in RLE compression.
NONE: No log data compression is used. This is the default value.
RLE: Log data compression is performed using run-length encoding (RLE).

For more details about log compression, see Log compression.

DEALLCT

Specifies the length of time that an allocated archive read tape unit is allowed to remain unused before it is deallocated. You are recommended to specify the maximum possible values, within system constraints, for both options to achieve the optimum performance for reading archive tapes.

This, together with the MAXRTU parameter, allows IBM® MQ to optimize archive log reading from tape devices.

The possible values are:

integer: Specifies the maximum time in minutes, in the range 0 through 1439. Zero means that a tape unit is deallocated immediately.
NOLIMIT or 1440: Indicates that the tape unit is never deallocated.

MAXARCH

Specifies the maximum number of archive log volumes that can be recorded in the BSDS. When this number is exceeded, recording begins again at the start of the BSDS.

Use a decimal number in the range 10 through 1000.

MAXCNOFF

Maximum number of concurrent log offload tasks.

Specify a decimal number between 1 and 31. If no value is specified the default of 31 applies.

Configure a number lower than the default if your archive logs are allocated on a tape device, and there are constraints on the number of such devices that can be concurrently allocated to the queue manager.

MAXRTU( integer )

Specifies the maximum number of dedicated tape units that can be allocated to read archive log tape volumes. This overrides the value for MAXRTU set by CSQ6LOGP in the archive system parameters.

This, together with the DEALLCT parameter, allows IBM MQ to optimize archive log reading from tape devices.

Note:

The integer value can be in the range 1 - 99.
If the number specified is greater than the current specification, the maximum number of tape units allowable for reading archive logs increases.
If the number specified is less than the current specification, tape units that are not being used are immediately deallocated to adjust to the new value. Active, or premounted, tape units remain allocated.
A tape unit is a candidate for deallocation because of a lowered value only if there is no activity for the unit.
When you are asked to mount an archive tape and you reply CANCEL, the MAXRTU value is reset to the current number of tape units.
For example, if the current value is 10, but you reply CANCEL to the request for the seventh tape unit, the value is reset to six.

WRTHRSH

Specifies the number of 4 KB output buffers to be filled before they are written to the active log data sets.

The larger the number of buffers, the less often the write takes place, and this improves the performance of IBM MQ. The buffers might be written before this number is reached if significant events, such as a commit point, occur.

Specify the number of buffers in the range 1 through 256.

ZHYWRITE

Specifies whether writes to the active logs are made with zHyperWrite being enabled. The active log datasets need to be on zHyperWrite capable volumes for zHyperWrite to be enabled.

For more information on enabling active logs with zHyperWrite, see Using zHyperWrite with IBM MQ active logs.

The value can be:

NO: zHyperWrite is not enabled.
YES: zHyperWrite is enabled.