Correcting bad pointers

The cause of bad pointers is typically:

• Failure to run database backout
• Failure to perform emergency restart
• Omitting a log during backout or recovery

The normal way to correct a bad pointer is to perform recovery. However, some cases exist in which a bad pointer can be corrected through reorganization. A description of the circumstances in which this can or cannot be done is as follows:

• PC/PT pointers. The HD Unload utility issues unqualified GN calls to read a database. If the bad pointer is a PC or PT pointer, DL/I will follow the bad pointer and the GN call will fail. Therefore, reorganization cannot be used to correct PC or PT pointers.
• LP/LT pointers. LP and LT pointers are rebuilt during reorganization. However, DL/I can follow the LP pointer during unload. If the logical child segment contains a direct LP pointer and the logical parent's concatenated key is not physically stored in the logical child segment, DL/I follows the bad LP pointer to construct the logical parent's concatenated key. This causes an ABEND.
• LP pointer. When DBR= is specified for pre-reorganization and the database has direct LP pointers, the HD Unload utility saves the old LP pointer. Bad LP pointers produce an error message (DFS879) saying a logical child that has no logical parent exists.
• LP pointer. When DBIL= is specified for pre-reorganization of a logical child or parent database, the utilities that resolve LP pointers use concatenated keys to match logical parent and logical child segments. New LP pointers are created.