Oracle Deadlock Causes Explained

There are several reasons that can cause a deadlock in Oracle databases.

1. Concurrency in transactions: when multiple transactions access the same resource in a database simultaneously, deadlocks can occur. For instance, if transaction A locks resource X and requests resource Y, while transaction B locks resource Y and requests resource X, it can lead to a deadlock.
2. Lock timeout: If a transaction is waiting to obtain a lock for longer than the maximum waiting time set by the system, it could potentially lead to a deadlock. This often occurs when a transaction is holding onto resources for an extended period without releasing them, causing other transactions to be unable to execute properly.
3. If the granularity of locks is too fine in the database design, meaning each transaction locks only a small amount of data, it will increase the likelihood of deadlock. This is because it can lead to multiple transactions simultaneously requesting different resources, potentially causing a deadlock.
4. Deadlock can occur when multiple transactions are competing for the same resource. For example, if transaction A locks resource X and requests a lock on resource Y, while transaction B locks resource Y and requests a lock on resource X, a deadlock can result.
5. Lack of a proper locking order: If transactions do not follow a certain rule when acquiring locks, such as obtaining them in the order of resources, it can lead to the occurrence of deadlocks. This could result in a situation of circular waiting, ultimately resulting in deadlocks.

The aforementioned are some common causes of deadlocks in Oracle databases, but the actual situation may be more complex, requiring analysis and resolution of deadlock issues based on specific application scenarios and database designs.