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Determining the Size of the Alternative Log Data Sets on z/OS

PowerExchange uses DCB attributes to allocate alternative log data sets on z/OS.

On z/OS, PowerExchange uses the following DCB attributes to allocate alternative log data sets:

Block size (BLKSIZE) is 27998.

Data set organization (DSORG) is PS.

Record format (RECFM) is VB.

Record length (LRECL) is the value of the RECLEN parameter in the TRACING statement.

You can use the following formulas to calculate the primary space and secondary space, in blocks, of an alternative log data set:

primary space = log_size / 27998 
secondary space = primary_space / 10

These formulas include the following variables:

log_size is the value that is specified for the SIZE parameter in the TRACING statement, converted from megabytes to bytes.

primary_space is the log_size divided by 27998, where 27998 is the block size in bytes.

secondary_space is the primary space divided by 10.

For example, if you specify 100 for the SIZE parameter, use the following formulas to calculate primary space and secondary space:

primary space = 104,857,600 / 27998 = 3745 blocks
secondary space = 3745 / 10 = 374 blocks