Smart-large-object locks

Locks on a CLOB or BLOB column are separate from the lock on the row. Smart large objects are locked only when they are accessed. When you lock a table that contains a CLOB or BLOB column, no smart large objects are locked. If accessed for writing, the smart large object is locked in update mode, and the lock is promoted to exclusive when the actual write occurs. If accessed for reading, the smart large object is locked in shared mode. The database server recognizes the transaction isolation mode, so if Repeatable Read isolation level is set, the database server does not release smart-large-object read locks before end of transaction.

When the database server retrieves a row and updates a smart large object that the row points to, only the smart large object is exclusively locked during the time it is being updated.