If you use the FTP engine in a FILENAME statement to transfer a large data set to a z/OS system, the default space allocations might not be large enough for your data. To allocate a larger data set, use the SITE command with the options PRI for primary space and SEC for secondary space in your FILENAME statement. Here is an example:

The default unit of space is tracks (TRK). The example uses CYL, which causes the primary and secondary space allocations to be in cylinders.