Unflagged Protection Violations

Protection violations typically occur when a process tries to access a memory location that lies outside the memory allocated to that process for the type of access it is attempting. Clearly the process miscalculated the location it wants to access.

However, if the same process moves, is rearranged in memory, or grows in size, the memory location might eventually lie in the range of the process. In such a case, the process would not give rise to a protection violation even though we would like it to.

If this is the case, the primary effect is that a statement in the program returns an incorrect result. If the application does not use that result, you will not notice a problem. However, if subsequent execution relies on the value returned by that statement, the program might exhibit unexpected behavior. Possible secondary effects can be split into two categories depending on the memory area that your program modifies:

• If the memory area lies in an unprotected COBOL system area, the COBOL system might exhibit unexpected behavior, including that resulting from executing data as if it were procedure. This could lead to a general protection violation or infinite loop.
• If the memory area lies in the program area, the program could produce incorrect results or fail at a later point as a result of a legitimate access to the memory area that had previously been corrupted.