Nonstop Database, HiRDB Version 9 Description
HiRDB provides the following five lock modes for each type of locked resource (such as table or page):
- Shared mode (PR: Protected Retrieve)
Only referencing by other transactions is allowed.
- Exclusive mode (EX: EXclusive)
One transaction monopolizes the locked resource and does not allow referencing, adding, updating, or deletion by other transactions.
- Shared retrieval mode (SR: Shared Retrieve)
Only referencing is allowed. Other transactions are allowed to perform referencing, adding, updating, and deletion of the locked resource.
- Shared update mode (SU: Shared Update)
If the lock is applied to a certain resource in the exclusive mode, the shared update mode applies to the resources above that locked resource; referencing, adding, updating, and deletion can be performed by other transactions.
- Protected update mode (PU: Protected Update)
Referencing, adding, updating, and deletion can be performed; referencing only can be performed by other transactions. Unlike modes 1-4, this mode occurs as a result of lock mode transition.
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