Accessing z/OS files through IMS: GSAM

GSAM enables IMS batch application programs and BMPs to access a sequential z/OS® data set as a simple database. The z/OS access methods that GSAM can use are BSAM and VSAM. A GSAM database is a z/OS data set record that is defined as a database record. The record is handled as one unit; it contains no segments or fields and the structure is not hierarchic. GSAM databases can be accessed by z/OS, IMS, and CICS®.

In a CICS environment, an application program can access a GSAM database from either a Call DL/I (or EXEC DLI) batch or batch-oriented BMP program. A CICS application cannot, however, use EXEC DLI to process GSAM databases; it must use IMS calls.

You commonly use GSAM to send input to and receive output from batch-oriented BMPs or batch programs. To process a GSAM database, an application program issues calls similar to the ones it issues to process a full-function database. The program can read data sequentially from a GSAM database, and it can send output to a GSAM database.

GSAM is a sequential access method. You can only add records to an output database sequentially.