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The record no longer reflects the first transaction, as if it had never taken place. A simple way to prevent this is to lock the file whenever a record is being modified by any user, so that no other user can save data. This prevents records from being overwritten incorrectly, but allows only one record to be processed at a time, locking out ...
The stateless nature of HTTP makes locking infeasible for web user interfaces. It is common for a user to start editing a record, then leave without following a "cancel" or "logout" link. If locking is used, other users who attempt to edit the same record must wait until the first user's lock times out. HTTP does provide a form of built-in OCC.
In databases and transaction processing, two-phase locking (2PL) is a pessimistic concurrency control method that guarantees conflict-serializability. [1] [2] It is also the name of the resulting set of database transaction schedules (histories).
A lock value block is associated with each resource. This can be read by any process that has obtained a lock on the resource (other than a null lock) and can be updated by a process that has obtained a protected update or exclusive lock on it. It can be used to hold any information about the resource that the application designer chooses.
IS locks conflict with X locks, while IX locks conflict with S and X locks. The null lock (NL) is compatible with everything. To lock a node in S (or X), MGL has the transaction lock on all of its ancestors with IS (or IX), so if a transaction locks a node in S (or X), no other transaction can access its ancestors in X (or S and X). This ...
File locking is a mechanism that restricts access to a computer file, or to a region of a file, by allowing only one user or process to modify or delete it at a specific time, and preventing reading of the file while it's being modified or deleted.
To reduce contention for table blocks due to delete, select or update statements, reduce the number of rows per block. This can be done by using a smaller block size. To reduce contention for table blocks due to insert statements, increase the number of freelists, or buffer frames.
MySQL (/ ˌ m aɪ ˌ ɛ s ˌ k juː ˈ ɛ l /) [6] is an open-source relational database management system (RDBMS). [6] [7] Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, [1] and "SQL", the acronym for Structured Query Language.