Accessing databases with your CICS application program

When designing your program, consider the type of data it must access. The type of data depends on the operating environment.

The data from IMS and Db2 for z/OS® databases, and z/OS files, that is available to CICS® online and IMS batch programs is shown in the following table.

Table 1. The data that your CICS program can access
Type of program	IMS databases	Db2 for z/OS databases	z/OS files
CICS online	Yes¹	Yes²	Yes³
DB batch	Yes	Yes³	Yes
Notes: Except for Generalized Sequential Access Method (GSAM) databases. GSAM enables batch programs to access a sequential z/OS data set as a simple database. IMS does not participate in the call process. Access through CICS file control or transient data services.

Also, consider the type of database your program must access. As shown in the following table, the type of program you can write and database that can be accessed depends on the operating environment.

Table 2. Program and database options in the CICS environments
Environment¹	Type of program you can write	Type of database that can be accessed
DB batch	DB batch	Db2 for z/OS² DL/I Full-function GSAM z/OS files
DBCTL	BMP	Db2 for z/OS DEDBs Full-function GSAM z/OS files
DBCTL	CICS online	Db2 for z/OS² DEDBs Full-function z/OS files (access through CICS file control or transient data services)
Notes: A CICS environment, or CICS remote DL/I environment also exists and is also referred to as function shipping. In this environment, a CICS system supports applications that issue DL/I calls but the CICS system does not service the requests itself. The CICS environment function ships the DL/I calls to another CICS system that is using DBCTL. For more information on remote DL/I, see CICS Transaction Server for z/OS IMS Database Control Guide. IMS does not participate in the call process.

The types of databases that can be accessed are:

Full-Function Databases
Full-function databases are hierarchic databases that are accessed through Data Language I (DL/I). DL/I calls enable application programs to retrieve, replace, delete, and add segments to full-function databases. CICS online and BMP programs can access the same database concurrently (if participating in IMS data sharing); an IMS batch program must have exclusive access to the database (if not participating in IMS data sharing).

All types of programs (batch, BMPs, and online) can access full-function databases.
Fast Path DEDBs
Data entry databases (DEDBs) are hierarchic databases for, and efficient access to, large volumes of detailed data. In the DBCTL environment, CICS online and BMP programs can access DEDBs.
Db2 for z/OS Databases
Db2 for z/OS databases are relational databases. Relational databases are represented to application programs and users as tables and are processed using a relational data language called Structured Query Language (SQL). Db2 for z/OS databases can be processed by CICS online transactions, and by IMS batch and BMP programs.

Related Reading: For information on processing Db2 for z/OS databases, see DB2® for z/OS Application Programming and SQL Guide.
GSAM Databases
Generalized Sequential Access Method (GSAM) is an access method that enables BMPs and batch programs to access a flat sequential z/OS data set as a simple database. A GSAM database can be accessed by z/OS or CICS.
z/OS Files
CICS online and IMS batch programs can access z/OS files for their input, processing, or output. Batch programs can access z/OS files directly; online programs must access them through CICS file control or transient data services.