GSAM databases
GSAM databases are sequentially organized databases that are designed to be compatible with z/OS® data sets.
GSAM databases have no hierarchy, database records, segments, or keys. GSAM databases can be in a data set previously created or in one later accessed by the z/OS access methods VSAM or QSAM/BSAM. GSAM data sets can use fixed-length or variable-length records when VSAM is used, or fixed-length, variable-length, or undefined-length records when QSAM/BSAM is used.
If VSAM is used to process a GSAM database, the VSAM data set must be entry sequenced and on a DASD. If QSAM/BSAM is used, the physical sequential (DSORG=PS) data set can be placed on a DASD or tape unit. If BSAM is used, the GSAM data sets can be defined as z/OS large format data sets by specifying DSNTYPE=LARGE on the DD statements.
GSAM supports DFSMS striped extended-format data sets for both VSAM and BSAM.
GSAM database data sets can be allocated in the extended addressing space (EAS) of an extended address volume (EAV).
Restriction: GSAM databases cannot be used with CICS® applications.
Because GSAM databases are supported in a DCCTL environment, you can use them when you need to process sequential non-IMS™ data sets using a BMP program.
GSAM databases are loaded in the order in which you present records to the load program. You cannot issue DLET and REPL calls against GSAM databases; however, you can issue ISRT calls after the database is loaded but only to add records to the end of the data set. Records are not randomly added to a GSAM data set.
Although random processing of GSAM and SHSAM databases is possible, random processing of a GSAM database is done using a GU call qualified with a record search argument (RSA). This processing is primarily useful for establishing position in the database before issuing a series of GN calls.
Although SHSAM and SHISAM databases can be processed in any processing region, GSAM databases can only be processed in a batch or batch message processing region.
The following IMS options do not apply to GSAM databases:
- Logical relationships
- Secondary indexing
- Segment edit/compression exit routine
- Field-level sensitivity
- Data Capture exit routines
- Logging or reorganization
- Multiple data set groups
For more information about GSAM data sets and access methods, including
information about the GSAM use of striped extended-format data sets,
see Processing GSAM databases
in IMS Version
13 Application Programming.
For more information about z/OS data sets, see z/OS DFSMS: Using Data Sets, as well as the z/OS DFSMShsm, DFSMSdss, and DFSMSdfp storage administration guides and references.