What are deadlocks in Oracle?
Ava Richardson
Updated on June 06, 2026
A deadlock occurs when two or more sessions are waiting for data locked by each other, resulting in all the sessions being blocked. Oracle automatically detects and resolves deadlocks by rolling back the statement associated with the transaction that detects the deadlock.
How do you fix deadlocks?
Deadlock frequency can sometimes be reduced by ensuring that all applications access their common data in the same order – meaning, for example, that they access (and therefore lock) rows in Table A, followed by Table B, followed by Table C, and so on.
What is deadlock in Oracle with example?
In a database, a deadlock is a situation in which two or more transactions are waiting for one another to give up locks. For example, Transaction A might hold a lock on some rows in the Accounts table and needs to update some rows in the Orders table to finish.
How deadlock is fixed in Oracle?
Resolving Oracle deadlocks
- Tune the application – Single-threading related updates and other application changes can often remove deadlocks.
- Add INITRANS – In certain conditions, increasing INITRANS for the target tables and indexes(adding slots to the ITL) can relieve deadlocks.
What are the different types of locks in Oracle?
There are five different types of locks in Oracle, and they are: exclusive, shared, shared row exclusive, row shared, and row exclusive….Exercises
- What is a lock?
- Describe the meaning of a shared lock and an exclusive lock.
What causes deadlocks in SQL Server?
A deadlock occurs when 2 processes are competing for exclusive access to a resource but is unable to obtain exclusive access to it because the other process is preventing it. SQL Server automatically detects when deadlocks have occurred and takes action by killing one of the processes known as the victim.
What is the difference between lock and deadlock?
Lock wait timeouts and deadlocks both arise from certain locking mechanisms. A deadlock happens when multiple lock waits happen in such a manner that none of the users can do any further work. For example, the first user and second user both lock some data. Then each of them tries to access each other’s locked data.
How does deadlock work?
A deadlock occurs when the first process locks the first resource at the same time as the second process locks the second resource. The deadlock can be resolved by cancelling and restarting the first process.
