Read write locks

Simple Locking:

  • Two main types of locks can be requested:
    • Shared lock: Read lock i.e. Any other TX can read but not write
    • Exclusive lock: Write lock i.e. No other TX can read or write

Multiple Locking:

  • Two Phase Locking (2PL) is a concurrency control method that guarantees serializability.
    • A Growing/Expanding/First Phase: locks are acquired and no locks are released.
    • A Shrinking/Contracting/Second Phase: locks are released and no locks are acquired.