Data consistency

Data consistency in multi-user mode

The FASTPAM access method does not provide a synchronization mechanism for shared access to a file (shared-update mode). Appropriate synchronization routines must therefore be supplied by the user if no such routines are included in the software product being used. If FASTPAM, UPAM and DIV applications are all operating in shared-update mode, a common synchronization mechanism must be used for all accesses.

Data consistency following a system crash

If an error occurs during an ACCESS FILE job, it is not possible specify whether and how much data has been transferred. The writing of a block cannot be treated as an atomic operation. The contents of the file may be inconsistent in such cases.