It is possible to use a user variable xxxx in RUNSYSIN member similarly as a variable in a batch job. The user variable name xxxx needs to be prefixed with VAR and is addressed as &VARxxxx keyword with a value assigned after the equal sign (=), quoted if it contains blanks.
There are up to 20 user variables for substitution. Each user variable name can have up to 16 characters.
If substitution is in effect, the variable name and value can be built from other variables.
The value length cannot exceed the length of the actual variable name + 1 (for an ampersand). The symbol substitution service enforces this rule to prevent buffer overruns.
Additional Information :
The complete description can be found from CA Solve:Access Session Management Reference Guide - Chapter 3 : Initializing Your Region Using the SOLVE Program