A lock upgrade or downgrade occurs when a JADE session has an object locked, and requests a lock with a different type or duration.
An upgrade means that the request is for a type or duration with a greater strength. A downgrade means a type or duration of lower strength is requested.
The strength of the various lock types, from lowest to highest, is as follows.
Shared
Reserve
Update
Exclusive
For duration, session duration is stronger than transaction duration.
Locks are not released while being upgraded or downgraded, with one exception: when a shared lock is being upgraded to an update lock, as described in the following section.