An exec running in a non-TSO environment can use the REXXIN data set to read data from. You must specify REXXTSO(NO) and REXXIN(YES) in the check definition in order to use a REXXIN data set. Typically, a check would use a REXXIN data set when it has a lot of input parameter data.

TSO environment REXX checks can use input data sets, see Using input data sets in a TSO-environment REXX check.

In order to get consistent results from your REXX checks, IBM® suggests that the exec has exclusive access to the REXXIN data set. If the system cannot allocate or use a requested REXXIN data set, the REXX check does not run successfully.