Lock-Based Protocols(Cont) Example of a transaction performing locking: T1: lock-X(B) lock-S(A) read(B read(A) B:=B-50 unlock(A) write (B) lock-S(B) unlock(B) read(B) lock-X(A unlock( B); read(A) display(A+B) A:=A+50 write(A) unlock(B) Database System Concepts 3rd Edition 16.4 OSilberschatz, Korth and SudarshanDatabase System Concepts 3 16.4 ©Silberschatz, Korth and Sudarshan rd Edition Lock-Based Protocols (Cont.) Example of a transaction performing locking: T1: lock-X(B) T2 : lock-S(A) read (B) read (A) B:=B-50 unlock(A) write(B) lock-S(B) unlock(B) read (B) lock-X(A) unlock(B); read(A) display(A+B) A:=A+50 write(A) unlock(B)