When any COBOL-DB2 program is pre-compiled, the current timestamp is inserted in the DBRM and if the DBRM is binded to a package then the timestamp is further copied to a package. Similarly, the timestamp is also inserted in the load module during the compilation process.
When any COBOL-DB2 program is executed, the system matches the timestamp of the load module with that in the DBRM/package, if there is mismatch then the program fails.
In case DBRM directly binds to a plan, we need to bind both the plans - PLANA and PLANB again even if only the subprogram has gone through the changes and not the main program. This is because during the execution of the main program the system will check for the consistency of timestamp between DBRM and load module. However, if we are using DBRM-package-plan combination then there is no need to bind the plan of the main program PLANA again.