- Insertion
- 2PL: DBMS secures exclusive write-lock
- TOA: op_TS(X) set to TS(creating transaction)
- Deletion
- 2PL: as insert
- TOA: waits to ensure later transactions don’t access
- Phantom problem
- Record being inserted matches inclusion conditions
- of another transaction
(e.g. selection by dno=5) - Locking doesn’t guarantee inclusion
(need index locking)
In Focus
4.2.11. Updates