Avoiding storage violations

CICS® provides three facilities that help to prevent storage violations.

CICS subsystem storage protection
prevents user application programs from directly overwriting CICS code and control blocks.
Transaction isolation
prevents a user transaction from directly overwriting user application storage of other transactions.
Command protection
prevents CICS, when processing an EXEC CICS command, from overwriting storage that the issuing transaction could not itself directly overwrite.

Even if your system uses all the CICS storage protection facilities, CICS storage violations can occur in certain circumstances in systems using storage protection. For example:

To gain the full benefit of CICS storage protection, you need to examine the storage needs of individual application programs and control the storage key definitions that are used.

When CICS detects and prevents an attempted storage violation, the name of the abending program and the address of the area it tried to overwrite are passed to the program error program (DFHPEP). For programming information about DFHPEP, see the CICS Customization Guide.

If a storage violation occurs in your system, please read the rest of this section.

Related concepts
Overview of CICS storage protection and transaction isolation
Causes of protection exceptions
Two kinds of storage violation
Related tasks
Defining the storage key for applications
Selecting the execution and storage key
Using transaction isolation
Worksheet for transaction abends
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