Partitioned hierarchic direct access method (PHDAM)
Partitioned hierarchic indexed direct access method (PHIDAM)
VSAM or OSAM
Fast Path
Data entry database (DEDB)
VSAM
Consider the following points regarding database compression:
Typically, HISAM database segments are not good candidates for compression. If you compress a HISAM database record that completely fits in the same logical record, actual DASD savings are minimal: the compression percentage achieved does not reduce the number of logical records that are stored on DASD. The only effect of compressing these records is that each logical record on DASD contains additional wasted free space.
If HISAM database records tend to span more than one logical record and use overflow, compression can reduce the amount of DASD that is required by reducing the amount of overflow space being used. Never compress a HISAM root-only database because no DASD savings can be achieved.
Because IMS does not allow you to code a compression exit in a simple hierarchic indexed sequential access method (SHISAM) or hierarchic sequential access method (HSAM) DBD, Data Packer cannot compress SHISAM or HSAM databases.