Suppose your program is ready to process the next record, but VSAM is still trying to obtain that record. (The next record is not yet read in from the direct access device.) You might need to stop execution of the program and wait for VSAM to complete reading in the record. The CHECK macro stops executing the program until the operation in progress is complete. You must issue a CHECK macro after each request for an RPL. If you attempt another request without an intervening CHECK, that request is rejected.

Once the request is completed, CHECK releases control to the next instruction in your program, and frees up the RPL for use by another request.