Selecting the execution and storage key
When you are running CICS® with
storage protection, the majority of your application programs should
execute in user key, with all their storage obtained in user key.
You only need to define EXECKEY(CICS) on program definitions, and
TASKDATAKEY(CICS) on the associated transaction definitions, for those
programs that use facilities that are not permitted in user key, or
for any special system-type
transactions or vendor packages.
About this task
You should only specify TASKDATAKEY(CICS) for those transactions where all the component programs have EXECKEY(CICS), and for which you want to protect their task lifetime and working storage from being overwritten by user-key applications. For example, the CICS-supplied transactions such as CEDF are defined with TASKDATAKEY(CICS).
Note that you cannot specify EXECKEY(USER) on any programs that form part of a transaction defined with TASKDATAKEY(CICS) because, in this situation, a user-key program would not be able to write to its own working storage. Transactions abend with an AEZD abend if any program is defined with EXECKEY(USER) within a transaction defined with TASKDATAKEY(CICS), regardless of whether storage protection is active.
You cannot define a program so that it inherits its caller's execution key. The execution key and data storage keys are derived for each program from its program and associated transaction resource definitions respectively, which you either specify explicitly or allow to default; the default is always user key. Table 1 summarizes the various combinations of options.
| EXECKEY | TASKDATAKEY | Recommended usage and comments |
|---|---|---|
| USER | USER | For normal applications using the CICS API |
| USER | CICS | Not permitted. CICS abends any program defined with EXECKEY(USER) invoked under a transaction defined with TASKDATAKEY(CICS). |
| CICS | USER | For programs that need to issue restricted MVS™ requests or modify CICS-key storage. |
| CICS | CICS | For transactions (and component programs) that function as extensions to CICS, such as the CICS-supplied transactions, or which require the same protection. |