A row lock is a table-row write lock that allows the holding transaction to write to any column of a locked row. Only one holder of this lock can exist at a time. A write-intent lock is a prerequisite; the transaction must hold a write-intent lock before the lock manager grants it a row lock.
A table-row write lock allows the holding transaction to write to any column of locked row. This lock cannot be granted without the requesting transaction first holding the write intent lock. Row write locks are exclusive locks; only one transaction can hold a write lock on a row at any time. Once a transaction acquires a write lock, requests to lock the row by other transactions are denied.
Row locks exist only during row deletions. The RLV store is an append-only store, meaning that every write action results in a new row appended to the store. INSERT statements append a new row to the store, as do UPDATE statements. The RLV store considers an UPDATE to be a DELETE followed by an INSERT. Before a row is deleted, either in the context of a DELETE or UPDATE statement, the database takes out a row-level lock.