Compaction

A magnetic tape subsystem that uses tape cartridges and has compaction capabilities can record data in either of two formats: compacted format or standard, uncompacted format. The recording format is specified in the TRTCH parameter of the JCL DD statement, the dynamic allocation text units, or the DCB macro. If none of these sources specify the recording format when writing the first data set on a volume, OPEN uses the specification in the DEVSUPxx member in SYS1.PARMLIB, which is set by the system programmer. Table 1 lists the parameters.