CAY6383E REGION REQUESTED UNAVAILABLE when the validating JCL has REGION=16M coded.
The region specified on the statement is larger than the private area below the 16 MB line.
Decrease the region size on the offending statement.
When REGION=n is coded, JCLCheck assumes that the application requires X amount of storage, and checks the storage control block to see if there's enough storage to satisfy the job. If there's not enough storage, error message "CAY6383E Region requested unavailable" is issued. (This logic applies only to storage requested below 16M.) When the JCL is actually executed, the job will complete successfully if the job used less amount of storage than specified on the REGION= parameter.
JCLCheck Workload Automation release 12.0
Set SYS1.PARMLIB member SMFLIMxx to NOLIMIT for jobs below the line will help to eliminate error CAY6383E.
Also error CAY6383E may be suppressed or reduced to a Warning or Informational.