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Locks and Locking
Michal Šimoník
misimonik@gmail.comhttp://www.michalsimonik.com
Independent consultant
+11 years in IT+10 years with Oracle
Database ArchitectData Modeling and TuningSQL TuningDatabase TroubleshootingConsulting
Michal Šimoník© 2015
About me
Oracle Database
Architecture
Michal Šimoník© 2015
Oracle Locking system
Oracle Database
Architecture
● Oracle vs Others
● Things to know first ...
Michal Šimoník© 2015
Lock types
Oracle Database
Architecture
● DML locks
● DDL locks
● Internal locks and latches
Michal Šimoník© 2015
Row Locks (TX) and Table Locks (TM)
Oracle Database
Architecture
● Row Locks○ TX - Exclusive
● Table Locks○ RS: Row Share○ RX: Row Exclusive○ S: Share○ SRX: Share row exclusive○ X: Exclusive
Michal Šimoník© 2015
DDL Locks
Oracle Database
Architecture
● Exclusive DDL locks
● Share DDL locks
● Breakable parse locks
Michal Šimoník© 2015
Oracle RAC - Global Enqueue Service (GES)
Oracle Database
Architecture
GES maintains synchronization of● Dictionary cache● Library cache● Transaction locks● DDL locks
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