Definicja lock cumulation

Co znaczy LOCK CUMULATION:

Multiple placing of a lock.

A lock cumulation occurs when the name, argument, and lock mode of the elementary locks are all the same. The cumulation counter is increased by 1 after every subsequent cumulation, and is reduced by 1 every time a lock cumulation is released. The lock itself is released when the counter reaches 0.

There are the following types of locks:

Shared (read lock):

Multiple transactions can hold a read lock simultaneously (for the purposes of reading data; that is, the data is not changed)

Exclusive (write lock):

Simultaneous read or write locks on this object are rejected. Only the lock owner can place further locks. This is known as cumulation.

Exclusive but not cumulative lock:

With this type of lock, even the original user can only place it once.

Optimistic lock:

Behaves like a shared lock, but is converted into an exclusive lock when the data is actually changed.

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