LISTBC pre-allocate exit

Use the pre-allocate exit to allocate the user log data set instead of having LISTBC perform the allocation. If LISTBC allocates the user log, it uses the following data set attributes for both sequential data sets and members of a PDS:

RECFM: fixed-blocked
LRECL: 150
BLKSIZE: 1500
Primary tracks: 1
Secondary tracks: 2

If the MSGPROTECT operand is set to ON, the following data set attributes are used:

LRECL: 232
BLKSIZE: 2320
Primary tracks: 1
Secondary tracks: 2

For members of a PDS, LISTBC uses a value of 20 for the number of directory blocks.

If you require different allocation values for the user log, use the pre-allocate exit to allocate the data set. SEND and LISTBC require that the record format specify fixed-length records. Note that the maximum LRECL you can define is 150. However, with MSGPROTECT set to ON the maximum LRECL you can define is 232.