iX V6.5 (30391-90011)

Appendix D 647

Multiple Calls to DBLOCK

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.