HP 3000 Manuals HP 3000 Manuals
Conditional Locks During a DBLOCK, if TurboIMAGE/XL discovers a lock descriptor that is identical to one previously put into effect by the same user through the same access path, it ignores the latest lock descriptor. For example, the lock descriptor SALES:ACCOUNT = 89393899 is ignored if SALES:ACCOUNT = 89393899 was locked earlier on the same access path. However, it will not be ignored if a lock descriptor such as SALES: @ has been specified earlier. If multiple lock descriptors are specified with mode 6 (conditional data entry locking), TurboIMAGE/XL indicates how many locks have been applied when it returns (status element 1) to the calling process. It does not release the successful locks even though all the requested locks have not been applied. Because TurboIMAGE/XL ignores identical lock descriptors specified a second time, it is possible to call DBLOCK again with the same descriptor list (if the program has MR capability). Those lock descriptors that are already in effect will be ignored and the others will be tried again. The second element of the status array contains the number of descriptors successfully locked in each call. This technique will not cause deadlocks provided the lock descriptor list is not altered.