19.1 Accessing IMS databases through the ODBA ODBA uses the IMS database resource adapter (DRA) function to establish a connection to the IMS subsystem specified by IMSID or DBCTLID coded in the DRA startup table. ODBA consists of a startup table for each IMS system and a group of modules that make up the ODBA callable interface. The DRA startup table specifies how to connect to a particular IMS subsystem, such as the subsystem name and the number of threads allowed. The ODBA callable interface modules manage threads connecting an ODBA application to an IMS system and also provide some recovery services. They provide a set of Data Language/I (DL/I) database calls and system services calls. Application programs establish connections to IMS systems and make IMS database and system function calls using AERTDLI. The syntax is very similar to AIBTDLI. ODBA requires the use of the application interface block (AIB). The AIB is a storage area obtained by the application program and is passed to IMS as a parameter in the AERTDLI call list when the application program issues DL/I calls. For ODBA, the AIB also provides the area the application program uses to keep track of the thread token. ODBA applications use z/OS Resource Recovery Services (RRS) and its application programming interfaces (APIs) to invoke commit processing. Figure 19-1 shows application access to IMS using the ODBA interface. z/OS