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Introduction to Locks
Control concurrent access to a shared resource
Rows
- Ensure that only one session at a time updates a row
- Helps prevent lost updates
Objects (e.g. tables)
- Ensure that object not dropped or altered while in use
Other:
- Memory latches
- Data Dictionary locks
Oracle acquires locks transparently
Notes:
Locks are a mechanism that databases use to control shared access to a resource. “Resource” can be a table row (Oracle supports row-level locking), a database object (e.g. table or stored procedure) the data dictionary or even a memory area (in the case of memory, locks are actually called “latches”).