When multiple users attempt to simultaneously update a record, the database
locking model ensures that the update from each user succeeds as a unit, but
each update overwrites the previous update. An explicit (pessimistic) locking
model prevents unexpected loss of data updates and controls the workflow when
simultaneous updates from more than one user occur.
There are two locking models that can be used:
- Optimistic locking - A locking technique that allows simultaneous updates
and detects conflicts in updates when the record is committed. By default
ClearQuest uses optimistic locking.
- Pessimistic locking - A locking technique that guarantees exclusive access
to the record while it is being edited.
Optimistic locking
Pessimistic locking