Deciding Which TP Message Log Values to Use

The default values for TP message log parameters tell APPC/MVS to create a new message log for each TP instance that ends on error. Depending on the environment in which the TP will run, and the type of TP, you might specify different values for the TP message log.

For example, the defaults might be appropriate for a TP running in a production system; however, you could bypass the message log completely, to reduce I/O and storage use. If the TP encounters a problem, you can change the parameter values only when you attempt to re-create the problem and collect diagnostic information. In contrast, when the TP is running in a test environment, you can use the values that allow you to collect all messages for all instances of the TP, whether or not each instance ends successfully.

Table 1 lists the results of each possible combination of TP message log parameters. As you read through them to determine which combination best suits your needs, keep these facts in mind:

Writing all messages for each instance of a TP requires more I/O than writing messages only on error, or bypassing the log.
Having a new message log for each instance of a TP requires more storage than adding messages to a cumulative log, or reusing an existing log. The value of DATASET_STATUS determines whether the log is new, cumulative, or reused; this parameter and its possible values are discussed in more detail in Selecting the Type of Message Log.
Logging messages for a standard TP differs from logging messages for a multi-trans TP. The differences mainly affect which value you choose for MSGLIMIT, which is discussed in more detail in Choosing a Value for the MSGLIMIT Parameter.

Table 1. Combination of Parameters Used in TP Message Log Definition
	KEEP_ MESSAGE_ LOG	MESSAGE_ DATASET	DATASET_ STATUS	MSGLIMIT	MSGLEVEL
Bypass TP Message Log Method 1	NEVER	N/A	N/A	N/A	N/A
Bypass TP Message Log Method 2	N/A	N/A	N/A	0	N/A
Create New Log Each Time	ALWAYS	&SYSUID. &SYSWUID. &TPDATE. &TPTIME. JOBLOG	NEW	0 - 15,000	1,1 (all msgs.)
Create New Log Each Time (on error only)	ERROR	&SYSUID. &SYSWUID. &TPDATE. &TPTIME. JOBLOG	NEW	0 - 15,000	1,0 (msgs. on error)
Create Cumulative Log	ALWAYS	data set name	MOD	0 - 15,000	1,1 (all msgs.)
Create Cumulative Log (on error only)	ERROR	data set name	MOD	0 - 15,000	1,0 (msgs. on error)
Log Most Recent TP Instance	ALWAYS	data set name	OLD	0 - 15,000	1,1 (all msgs.)
Log Most Recent TP Instance (on error only)	ERROR	data set name	OLD	0 - 15,000	1,0 (msgs. on error)