suppose that a dbms recognizes increment,which increment an integervalued object by 1,and decrement as actions,in addition to reads and writes.A transaction that increments an objet need not known the value of the object;increment and decrement are versions of blind writes.in addition to shared and exclusive locks,tow special locks are supported:An object must be locked in I mode before incrementing it and locked in D mode before decrementing it .An I lock is compatible with another I or D lock on the same object,but not with S and X locks.

1. Illustrate how the use of I and D locks can increase concurrency.(show a schedule allowed by strict 2PL that only uses S and X locks. Explain how the use of I and D locks can allow more action to be interleaved,while continuing to follow strict 2PL) 2. Informally expalin how strict 2PL guarantees serializability even in the presence of I and D locks. (identify which pairs of actions conflict,in the sence the their relative order can a_ect the result,and show that the use of S,X,I and D locks according to Strict 2PL orders all conflicting pairs of actions to be the same as the order in some serial.