Usage requirements

The following requirements must be met in order to use the OSREQ macro successfully:

The caller must be in task mode, 31-bit addressing mode, primary addressing mode, problem or supervisor state, and any storage protect key. (Callers may not be in cross-memory mode.)
The calling program cannot hold any MVS locks.
All input and output parameters must be contained within the home address space and must be accessible in primary addressing mode.
The DB2 subsystem must be running and, if CICS is used, it must be connected to DB2. The installation is responsible for starting the DB2 subsystem and establishing the connection.
The call attachment facility is used by OAM in the MVS batch environment to connect to DB2 during the ACCESS call to OAM. After the connection is made to DB2, a thread is established (by OPEN) to plan CBRIDBS. The call to ACCESS should be invoked prior to any application DB2 activities occurring to allow synchronization with the OAM database activities. Synchronization is the responsibility of the application and is in the form of CLOSE, then OPEN, as described in the IBM Information Management Software for z/OS Solutions Information Center.
In the CICS, DSN Command Processor, and IMS environments, it is assumed that the connection to DB2 has already been made. Synchronization in CICS is accomplished through the use of the SYNCPOINT function (refer to the IBM Information Management Software for z/OS Solutions Information Center). In the TSO environment, synchronization is accomplished through the use of COMMIT and ROLLBACK functions, as described in the IBM Information Management Software for z/OS Solutions Information Center. In the IMS environment, synchronization is accomplished through the use of COMMIT and ROLLBACK functions (see the IBM Information Management Software for z/OS Solutions Information Center), or by the use of SYNC and ROLL/B call to IMS.
If you use JOBLIB or STEPLIB JCL statements in your application that include DB2 load modules, then the entire JOBLIB or STEPLIB concatenation must be assigned to authorized libraries. Because the OSREQ application programming interface runs in an authorized state, it must load the DB2 modules at the time the ACCESS function is invoked. MVS requires that all libraries in a concatenation must be authorized when the loading program is authorized.

Note: If an application invokes the OSREQ API without passing an IADDRESS, OAM assumes the application is running in one of the CAF supported environments, Batch, IMS, CICS, TSO, or DSN. If an application invokes the OSREQ API using the IADDRESS parameter, it will be assumed that the application has done the connection to DB2 and has loaded the appropriate DB2 module. Environments or invocations other than those listed in Table 1 in ACCESS—Initializing the OSREQ interface have not been tested by IBM and the results may be unpredictable. An example of an untested, unpredictable environment would be the DB2 Stored procedure environment.