In Oracle, a deadlock scenario can be generated when two or more transactions are waiting for each other to release locks on resources that they need in order to proceed. This can happen when one transaction holds a lock on a resource that another transaction also needs, and vice versa.
To intentionally create a deadlock scenario in Oracle, you can follow these steps:
- Start two separate sessions in Oracle.
- In session 1, perform an update operation on a table without committing the transaction.
- In session 2, perform an update operation on the same table that session 1 is working on, without committing the transaction.
- In session 1, try to update a different row in the same table that session 2 is working on.
- In session 2, try to update a different row in the same table that session 1 is working on.
At this point, both sessions will be waiting for each other to release the locks on the resources that they need to proceed. This will result in a deadlock scenario, where neither transaction can continue and the database system will need to resolve the deadlock by rolling back one of the transactions.
What is Oracle deadlock processing?
Oracle deadlock processing refers to the mechanisms and techniques used by Oracle database management systems to detect and resolve deadlocks. Deadlock occurs when two or more transactions are waiting for each other to release locks on resources that each transaction needs to continue executing.
Oracle uses a detection mechanism called the deadlock detection algorithm to identify deadlocks. Once a deadlock is detected, Oracle employs a method known as deadlock detection and resolution to resolve the deadlock. This can involve either rolling back one of the transactions involved in the deadlock or waiting for one of the transactions to release locks.
In some cases, Oracle may automatically resolve deadlocks by rolling back the transaction that has done the least amount of work or has been active for the shortest duration. However, in more complex situations, manual intervention may be required to resolve deadlocks.
Overall, Oracle deadlock processing ensures the integrity and consistency of the database by handling deadlocks efficiently and preventing them from impacting the performance of the system.
What is a deadlock and how does it occur in Oracle?
A deadlock is a situation where two or more transactions are waiting for each other to release locks on resources that they need to complete their transactions. As a result, none of the transactions can proceed, causing a deadlock.
In Oracle, a deadlock can occur when two or more transactions each hold locks on resources that the other transactions need to proceed. For example, Transaction A may be holding a lock on Table X and needs a lock on Table Y, while Transaction B may be holding a lock on Table Y and needs a lock on Table X. If neither transaction releases its lock on the resource it holds, a deadlock occurs.
Oracle automatically detects deadlocks and resolves them by rolling back the transaction that is least costly to undo. This allows the other transactions involved in the deadlock to continue processing. Developers can also take steps to prevent deadlocks from occurring, such as ensuring that transactions access resources in the same order to avoid circular dependencies.
What is Oracle deadlock session?
An Oracle deadlock session occurs when two or more sessions are waiting for each other to release locks on resources that they need to complete their transactions. This results in a situation where none of the sessions can proceed, causing a deadlock. Oracle automatically detects and resolves deadlocks by rolling back one of the transactions involved, allowing the other transaction to continue.
What is Oracle deadlock error code?
The common Oracle deadlock error code is ORA-00060.
