SHSAM databases

A simple HSAM (SHSAM) database is an HSAM database containing only one type of segment, a root segment. The segment has no prefix, because no need exists for a segment code (there is only one segment type) or for a delete byte (deletes are not allowed).

SHSAM databases can be accessed by z/OS® BSAM and QSAM because SHSAM segments contain user data only (no IMS prefixes). The ISRT, DLET, and REPL calls cannot be used to update. However, ISRT can be used to load an SHSAM database. Only GET calls are valid for processing an SHSAM database. These allow retrieval only of segments from the database. To update an SHSAM database, it must be reloaded. The situations in which SHSAM is typically used are explained in the introduction to this topic. Before deciding to use SHSAM, read the topic on GSAM databases, because GSAM has many of the same functions as SHSAM. Unlike SHSAM, however, GSAM files cannot be accessed from a message processing region. GSAM does allow you to take checkpoints and perform restart, though.

Although SHSAM databases can use the field-level sensitivity option, they cannot use any of the following options:

• Logical relationships
• Secondary indexing
• Multiple data set groups
• Variable-length segments
• Segment edit/compression exit routine
• Data Capture exit routines
• Logging, recovery, or reorganization