What is a deadlock in a database and how can it be prevented or resolved?

A deadlock in a database occurs when two or more processes or transactions are waiting for each other to release locks on resources, resulting in a deadlock situation where none of the processes can proceed.

Deadlocks are usually caused by improper usage of transactions and locking mechanisms within a database management system.

Prevention Strategies for Deadlocks:

• 1. Use proper indexing and query optimization to reduce the time locks are held.
• 2. Keep transactions short and avoid unnecessary locking of resources.
• 3. Set proper isolation levels for transactions to minimize conflicts.
• 4. Implement timeouts to automatically abort transactions that are taking too long.

Resolution Techniques for Deadlocks:

• 1. Detect deadlocks using database monitoring tools or system logs.
• 2. Kill one of the processes involved in the deadlock to break the deadlock cycle.
• 3. Retry the transaction after a short delay to see if the deadlock resolves itself.
• 4. In some cases, manually release locks on resources to resolve the deadlock.

By following these prevention strategies and resolution techniques, database administrators can effectively manage and mitigate deadlocks in a database.