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How does a DB lock work?
When data is locked, then that means that another database session can NOT update that data until the lock is released (which unlocks the data and allows other database users to update that data. Locks are usually released by either a ROLLBACK or COMMIT SQL statement.
How does MySQL connection work?
The MySQL Clients send connection requests to the MySQL Server. A connection request is simply a TCP-IP connect message sent to port 3306 on the server host machine. Receiver Thread. Incoming connection requests are queued and then processed by the receiver thread one by one.
Why is locking mandatory for ensuring consistency?
The task of the locking system is to manage access to resources shared by user databases, tables, pages and rows to guarantee the consistency of the shared data. Various types of locks are used to ensure that the database does not become inconsistent through concurrent update.
How does a lock work in a database?
In order to avoid this problem, database locks the data for the first user and allows him to update/delete the data. Once he is done with his update/delete, he COMMITs or ROLLBACK the transaction, which will release the lock on the data.
What does it mean to have a deadlock in SQL?
A deadlock is a situation in the database where one user or session is waiting for the lock to be acquired on the data, while another user or session is waiting for the first user or session to complete the transaction and release the lock. This means, waiting for acquiring lock forms a cycle and it will never release the lock at all.
Is the exclusive lock the same as the database lock?
However, in Oracle the exclusive lock is same as Database lock and does not allow others to use entire database. It will be helpful when some support update is being executed like upgrading to new version of software etc. File Level Locking : Here, entire database file will be locked.
How are DB sessions created in SQL Server?
A DB session is created when a user connects to the DB. Same user may connect to the DB multiple times and multiple DB sessions will be created for that user. It need not be different user connecting to the same DB. In different session, user may be trying to update the same data at the same time.