Considerations for executing commands in the background

When the TMP executes in the background, some TSO/E commands are processed differently than when they execute in the foreground. For example, a job that invokes the TMP in the background is authorized to execute the ACCOUNT command, if the "USER=" field is not specified. Therefore, for security reasons, you should either:
- RACF-protect or password-protect the UADS
- Write a JCL exit to limit access to the background TMP.
For more information about the differences in command processing in the background, see z/OS TSO/E User's Guide.
An unqualified data set name will not be prefixed with a user ID, because "no prefixing" of data set names is the default in the background. If you want a user ID prefixed to the data set names, and are not defined to RACF®, include the following command at the beginning of the SYSTSIN stream:
```
profile prefix(userid)
```
If you are defined to RACF, you do not have to include the profile prefix(userid) command in the SYSTSIN stream. Instead, specify USER=userid on the JOB card, and the user ID you specify is used as the prefix.

Read also the following item about the requirement that a user must have logged on and off at least once.
If your batch job uses commands or subcommands in the SYSTSIN stream that use user IDs not defined as TSO/E users (for example, SEND or RECEIVE), consider the following requirement:
The TMP requires user logon information found in either the user attribute data set SYS1.UADS, or the TSO/E segment of the RACF data base. This information is built through the LOGON and LOGOFF command. Therefore, it is required that each referenced user is defined to either UADS or to RACF, and has performed a LOGON and LOGOFF command at least once.