Intention exclusive lock (IX)

Intention exclusive (IX) lock is a type of lock used in database management systems (DBMS) to indicate that a transaction intends to acquire an exclusive lock on a higher-level resource, such as a table, while allowing other transactions to acquire shared locks on the same resource. It is a concept related to lock compatibility and concurrency control in databases.

Intention Exclusive Lock (IX lock):

An intention exclusive lock is used to signal the intent of a transaction to acquire an exclusive lock on a higher-level resource, such as a table or a page, while still allowing other transactions to acquire shared locks on that resource. IX locks are used to coordinate the acquisition of exclusive locks at a higher level.

For example, consider a scenario where multiple transactions want to modify different rows within a table:

🔺Transaction A intends to update Row 1 of the table and requests an intention exclusive lock on the table.

🔺The DBMS grants the IX lock to Transaction A, indicating its intention to acquire an exclusive lock on a specific row(s) within the table.

🔺Transaction B wants to update Row 2 of the same table and also requests an intention exclusive lock.

🔺The DBMS grants the IX lock to Transaction B as well since IX locks are compatible with each other.

🔺Transaction A then acquires an exclusive lock on Row 1, and Transaction B acquires an exclusive lock on Row 2.

🔺Both Transaction A and Transaction B can now modify their respective rows.

Intention exclusive locks allow multiple transactions to signal their intent to acquire exclusive locks on different parts of a resource. 

They facilitate coordination and prevent conflicts among transactions that want to acquire exclusive locks on specific subsets of a resource, such as rows within a table.