When choosing an algorithm for compacting a data set, selects either the unique source or object compaction table or selects the default general compaction table. You can identify data sets that you want to compact with unique source or object compaction tables by specifying the low-level qualifiers for those data sets when you specify the SETSYS SOURCENAMES and SETSYS OBJECTNAMES commands.
For generation data groups, uses the next-to-the-last qualifier of the data set name. uses the same compaction table for all blocks in each data set. The source compaction table is designed to compact data sets that contain programming language source code. The object compaction table is designed to compact data sets containing object code and is based on an expected frequency distribution of byte values.