Data Integrity with DB2 for z/OS

176 Data Integrity with DB2 for z/OS

6.1 DB2 attachment facilities

An attachment facility can be thought of as a required portal or gateway when a user request

to connect to a DB2 subsystem originates from certain environments. In order to

communicate with DB2 for z/OS from a Customer Information Control System (CICS),

Information Management System (IMS), Time Sharing Option (TSO), batch or WebSphere

(when using RRS) environment, a DB2 attachment facility is required to establish a session.

Attachment facilities are subcomponents of DB2 that run in the user’s address space.

CICS

The CICS attachment facility, language interface module DSNCLI, is provided by the CICS

product. It receives CICS application requests and passes them to DB2. Example 6-1 shows

the standard CICS command-level services that you can use.

Example 6-1 CICS command-level services used with the CICS attachment facility

EXEC CICS WAIT

EXEC CICS ABEND

By issuing DB2 commands, an authorized CICS terminal operator is able to control and

monitor DB2 and the attachment facility.

IMS

The IMS attachment facility, program interface DFSLI000, is required to access DB2 from an

IMS environment. It receives and interprets requests for access to DB2 databases using exits

provided by IMS subsystems. The IMS attachment facility also allows an authorized IMS

terminal operator the ability to issue DB2 commands such as starting and stopping DB2

databases.

TSO

The TSO attachment facility offers unique functionality. It is required for binding application

plans and packages and executing online DB2 functions. In fact, the CICS and IMS

attachment facilities depend on the TSO attachment facility for these functions.

Access to DB2 in the foreground through a TSO terminal or in batch mode through the TSO

terminal monitor program (TMP) can be accomplished with the TSO attachment facility. In

addition, two command processors are provided:

 DSN command processor: Primarily used for batch jobs, uses the TSO attachment facility

and runs as a TSO command processor

 DB2 Interactive (DB2I): An interactive connection to DB2 allowing users to run SQL

statements, issue DB2 commands, and run DB2 utilities using Interactive System

Productivity Facility (ISPF) panels

With the TSO attachment facility, load module DSNELI, access to DB2 is fairly simple. On the

other hand, this also means that an application has less control over the status of the

connections and, when using DSN services, applications running under the control of DSN.

Call attachment facility (CAF)

As the alternative attachment facility for TSO and batch applications, CAF supplies additional

connection functionality and greater control over the execution environment including:

 Explicit control over the status of the connection to DB2.

 Used with or without TSO TMP.