Summary of IMS database types and functions

The following table provides a summary of characteristics, functions, and options of the different types of IMS databases.

Database types

You can find information about the types of databases supported by IMS in the following table:
Table 1. Database types supported by IMS
Database type Access method Full-function database Fast Path database High Availability Large Database (HALDB)
HSAM Hierarchical Sequential Access Method Yes No No
HISAM Hierarchical Indexed Sequential Access Method Yes No No
SHSAM Simple Hierarchical Sequential Access Method Yes No No
SHISAM Simple Hierarchical Indexed Sequential Access Method Yes No No
GSAM Generalized Sequential Access Method Yes No No
HDAM Hierarchical Direct Access Method Yes No No
PHDAM Partitioned Hierarchical Direct Access Method Yes No Yes
HIDAM Hierarchical Indexed Direct Access Method Yes No No
PHIDAM Partitioned Hierarchical Indexed Direct Access Method Yes No Yes
PSINDEX Partitioned Secondary Index Database Yes No Yes
DEDB Data Entry Database (Hierarchical Direct Access) No Yes No
MSDB Main Storage Database (Hierarchical Direct Access) No Yes No

Summary of database characteristics

Table 2. Summary of database characteristics and options for database types
Characteristic HSAM HISAM HDAM PHDAM HIDAM PHIDAM DEDB MSDB
Hierarchical structures Yes Yes Yes Yes Yes Yes Yes No
Direct access storage Yes Yes Yes Yes Yes Yes Yes No
Multiple data set groups No No Yes Yes Yes Yes No No
Logical relationships No Yes Yes Yes Yes Yes No No
Variable-length segments No Yes Yes Yes Yes Yes Yes No
Segment Edit/Compression No Yes Yes Yes Yes Yes Yes No
Data Capture exit routines No Yes Yes Yes Yes Yes Yes No
Field-level sensitivity Yes Yes Yes Yes Yes Yes No No
Primary index No Yes No No Yes Yes No No
Secondary index No Yes Yes Yes Yes Yes Yes No
Logging, recovery, offline reorganization No Yes Yes Yes Yes Yes Yes Yes
VSAM No Yes Yes Yes Yes Yes Yes Not applicable
OSAM No No Yes Yes Yes Yes No Not applicable
QSAM/BSAM Yes No No No No No No Not applicable
Boolean operators Yes Yes Yes Yes Yes Yes Yes No
Command codes Yes Yes Yes Yes Yes Yes Yes No
Subset pointers No No No No No No Yes No
Uses main storage No No No No No No No Yes
High parallelism (field call) No No No No No No No Yes
Compaction Yes Yes Yes Yes Yes Yes Yes No
DBRC support Yes Yes Yes Required Yes Required1 Yes Not applicable
Partitioning support No No No Yes No Yes Yes No
Data sharing Yes Yes Yes Yes Yes Yes Yes No
Partition sharing No No No Yes No Yes Yes No
Block level sharing Yes Yes Yes Yes Yes Yes Yes No
Area sharing Not applicable Not applicable Not applicable Not applicable Not applicable Not applicable Yes Not applicable
Record deactivation No No No No No No Yes Not applicable
Database size Medium Medium Medium Large Medium Large Large Small
Online utilities No No No No No No Yes No
Online reorganization No No No Yes No Yes Yes No
Batch Yes Yes Yes Yes Yes Yes No No
Table notes:
  1. The IMS catalog is a PHIDAM database. Unlike other HALDB databases, the IMS catalog PHIDAM database does not require DBRC support. However, DBRC support is strongly recommended outside of test and development environments.