Which lock type is most restrictive?

The most restrictive lock type in a database management system, including Teradata, is the exclusive lock. An exclusive lock prevents other transactions from accessing the locked resource, ensuring that while one transaction holds the lock, no other transactions can read or write to that resource. This level of restriction is necessary in situations where the integrity of the data is critical, and changes must not be interrupted or influenced by other transactions.

In contrast, an access lock allows shared access, meaning multiple transactions can read the resource simultaneously. A read lock permits others to read the data but not write to it, while a write lock may allow writing but still can be overridden by an exclusive lock if it is held by another transaction. The exclusive lock’s ability to block all other operations makes it the most restrictive lock type, safeguarding the changes being made until they are fully committed.