Step 1. Know the rules for using system symbols in parmlib

Follow these rules and recommendations when using system symbols in parmlib:

1. Specify system symbols that:
   • Begin with an ampersand (&)
   • Optionally end with a period (.)
   • Contain 1-8 characters between the ampersand and the period (or the next character, if you do not specify a period).
   Note: Symbols are character strings and can only be used as such. Even though a character string can consist of only numeric characters, it cannot be used as a number. For example, a symbol cannot be used for the start or number value in a substring.
   If the system finds a system symbol that does not end with a period, it will substitute text for the system symbol when the next character is one of the following:

   • Null (the end of the text is reached)
   • A character that is not alphabetic, numeric, or special (@,#, or $).
   Recommendation: End all system symbols with a period. Omitting the period that ends a system symbol could produce unwanted results under certain circumstances. For example, if the character string (2) follows a system symbol that does not have an ending period, the system will process the (2) as substring syntax for the system symbol, regardless of how you intended to use the string in the command. For more information about substringing system symbols, see Using substrings of system symbols.
2. Use a small set of system symbols so they are easy to manage and remember.
3. Code two consecutive periods (..) if a period follows a system symbol. For example, code &DEPT..POK when the desired value is D58.POK and the substitution text D58 is defined to the system symbol &DEPT.
4. When using system symbols in data set name qualifiers, keep the rules for data set naming in mind. For example, if you use &SYSNAME as a data set qualifier, ensure that the substitution text begins with an alphabetic character.
5. Ensure that resolved substitution texts do not extend parameter values beyond their maximum lengths. For example, suppose that the following command is to start CICS®:

      S CICS,JOBNAME=CICS&SYSNAME.,...

   The resolved substitution text for &SYSNAME cannot exceed four characters because job names are limited to eight characters (the four characters in CICS plus up to four character in &SYSNAME). A substitution text of SYS1 is valid because it resolves to the job name CICSSYS1. However, a substitution text of SYSTEM2 is not valid because it resolves to the job name of CICSSYSTEM2, which exceeds the allowable maximum of eight characters.

6. If you use &SYSNAME, ensure that its substitution text is unique on each system. See Step 3. Determine where to specify the system name for more information.
7. Do not specify system symbols in the values on the OPI and SYSP parameters in the IEASYSxx parmlib member.
8. Do not specify any system symbols in parmlib members that do not support system symbol substitution. See Overview of parmlib members for information about the parmlib members that support system symbols.