HISAM databases

In a hierarchical indexed sequential access method (HISAM) database, as with an HSAM database, segments in each database record are related through physical adjacency in storage.

Unlike HSAM, however, each HISAM database record is indexed, allowing direct access to a database record. In defining a HISAM database, you must define a unique sequence field in each root segment. These sequence fields are then used to construct an index to root segments (and therefore database records) in the database.

HISAM databases are stored on direct-access devices. They can be processed using the virtual storage access method (VSAM) utility. Unlike HSAM, all DL/I calls can be issued against a HISAM database. In addition, the following options are available for HISAM databases:

• Logical relationships
• Secondary indexing
• Variable-length segments
• Segment edit/compression exit routine
• Data Capture exit routines
• Field-level sensitivity
• Logging, recovery, and reorganization