IMS attachment facility
The IMS attachment facility enables you to access Db2 from IMS.
The IMS attachment facility receives and interprets requests for access to Db2 databases by using exit routines that are part of IMS subsystems. An exit routine is a program that runs as an extension of Db2 when it receives control from Db2 to perform specific functions. Usually, IMS connects to Db2 automatically with no operator intervention.
In addition to Data Language I (DL/I) and Fast Path calls, IMS applications can make calls to Db2 by using embedded SQL statements. In the case of system failure, IMS coordinates recovery of both Db2 data and IMS data.
With proper planning, you can include Db2 in an IMS Extended Recovery Facility (XRF) recovery scenario.
With the IMS attachment facility, Db2 provides database services for IMS dependent regions. DL/I batch support allows any authorized user to access both IMS data and Db2 data in the IMS batch environment.
Application programming, system administration, and operations organizations can use the IMS attachment facility.
- Application programming
With the IMS attachment facility, Db2 provides database services for IMS dependent regions. DL/I batch support allows users to access both IMS data (DL/I) and Db2 data in the IMS batch environment, which includes:
- Access to Db2 and DL/I data from application programs.
- Coordinated recovery through a two-phase commit process.
- Use of the IMS extended restart (XRST) and symbolic checkpoint (CHKP) calls by application programs to coordinate recovery with IMS, Db2, and generalized sequential access method (GSAM) files.
IMS programmers who write the data communication portion of application programs do not need to alter their coding technique to write the data communication portion when accessing Db2; only the database portions of the application programs change. For the database portions, programmers code SQL statements to retrieve or modify data in Db2 tables.
To an IMS terminal user, IMS application programs that access Db2 appear identical to IMS.
Db2 supports this cross-product programming by coordinating database recovery services with those of IMS. Any IMS program uses the same synchronization and rollback calls in application programs that access Db2 data as they use in IMS application programs that access DL/I data.
Another aid for cross-product programming is the IMS DataPropagator licensed program, which enables automatic updates to Db2 tables when corresponding information in an IMS database is updated. This product also enables automatic updates to an IMS database when a Db2 table is updated.
- System administration and operations
An authorized IMS terminal operator can issue Db2 commands to control and monitor Db2. The terminal operator can also start and stop Db2 databases.
Even though you perform Db2 functions through IMS, you need the TSO attachment facility and ISPF to take advantage of the online functions supplied with Db2 to install and customize your system. You also need the TSO attachment facility to bind application plans and packages.