Functional benefits of DBCTL

The functional benefits that DBCTL offers are in the areas of:

Data availability

Previously, if you did not use DBCTL, and a database was unavailable when CICS® tried to schedule a program specification block (PSB), the transaction received a return code to say that the schedule has failed. DBCTL enables CICS to take advantage of the data availability that IMS™ provides; you can successfully schedule a PSB, even though some of the databases used in that PSB are unavailable.

Scheduling for database recovery is more flexible because database blocks (or CIs) that have had read or write errors are still available after a DBCTL restart.

See Enhanced scheduling for more information on data availability and the system service requests you can use in connection with it.

Batch message processing programs (BMPs)

Running batch jobs (both CICS shared database and "native" IMS batch jobs) as BMPs enables you to use system service requests, such as symbolic checkpoint (CHKP) and extended restart (XRST), and to access GSAM databases, which you could not do with CICS shared database. With BMPs, all logging goes to a single log (the IMS log), which eliminates the need for separate batch logs. BMPs also support automatic backout, and automatic restart from the last checkpoint (without requiring JCL changes). BMPs communicate directly with the DBCTL address space instead of accessing databases through CICS, and enable concurrent access to databases without the need to use IMS data sharing. Using BMPs gives a performance advantage compared with the same programs that ran as CICS shared database jobs, both in terms of the elapsed time of the batch jobs themselves, and in terms of transaction response and throughput, because they do not delay the CICS online workload as much. See Batch message processing programs (BMPs) for more information.

System service requests

Your CICS application programs can use the following IMS system service requests in addition to those related to data availability:

See Application programming for DBCTL for more information on using these requests.

Access to data entry databases (DEDBs)

Data entry databases (DEDBs) provide the same features as HDAM databases (with the exceptions of secondary indexing and logical relationships). They also have a number of advantages. Using DEDBs enables you to have very large databases with high availability. DEDBs are designed to provide efficient storage and fast online gathering, retrieval, and update of data, using VSAM entry sequenced data sets (ESDSs).

DEDBs are hierarchic databases that can contain up to 127 segment types. One of these segments is always a root segment. The remaining 126 segments can either be direct dependent (DDEP) segments, or 125 DDEP segments and one sequential dependent (SDEP) segment. A DEDB structure can have as many as 15 hierarchical levels.

DEDBs are made up of database records stored in a set of up to 240 areas. Each area contains a range of database records (which you can specify using the DEDB randomizing routine) that contain the entire logical structure for a set of root segments and their dependent segments. Areas are independent of each other, are individually recognized, can be accessed by multiple programs and DEDB utilities, are the basis for recovery procedures, and are largely transparent to application programs.

DEDBs provide the following advantages:

Related concepts
Benefits of using DBCTL
System availability benefits of DBCTL
Performance benefits of DBCTL
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