RECEIVE log data set pre-allocation exit

Each time a log data set is to be allocated, the RECEIVE pre-allocation exit, INMRZ21R, receives control. This exit may be invoked multiple times for each RECEIVE operation. This exit can allocate the log data set, modify the data set name, or take no action. If the exit chooses to allocate the data set, the exit must pass the file name back to the RECEIVE command. If the exit modifies the data set name, the RECEIVE command will then allocate the data set for the exit if the exit has not already done so.

Under normal operations, the RECEIVE command frees the log data sets automatically. Therefore, even if the exit allocated the log data set, the data set is freed when the command processor terminates normally.

During RECEIVE processing, the allocation of the log data set occurs after the RECEIVE command has begun reading the input file.

If the exit is to allocate the log data set, consider the following:

RECEIVE allocates the data set as NEW if it does not exist. This frees users from having to allocate the data set themselves.
RECEIVE allocates the data set with a disposition of NEW or MOD. The exit should also allocate the data set with a disposition of NEW or MOD.
If the exit allocates the data set as NEW, the data set must have the characteristics of a log data set. The characteristics of a log data set are:
- Record Format (RECFM) of VB
- Logical Record Length (LRECL) of 255
- Blocksize (BLKSIZE) of 3120

Errors during log processing do not normally terminate command processing. Instead, the command sets a return code of 4, indicating that an error occurred but the transmission was successful. If the exit gives a non-zero return code, RECEIVE does not terminate processing, but sets a return code of 4, indicating that the logging function encountered an error.