A foreign key link from the originating table back to the ID found on the P2K_AM_EXECUTIONS table.
The MEX_ID is the link to each execution of any report or update function and is often used as an indicator that a process has been run.
For example, on P2K_PR_DEPOSITS, the MEX_ID indicates what execution sent the deposit information to the bank for direct deposit (UPDISB) and the not null value is a flag that it should not be picked up in subsequent runs.
