Is Strict 2pl Deadlock Free? - Fixanswer

Conservative 2-PL – A.K.A Static 2-PL, this protocol requires the transaction to lock all the items it access before the Transaction begins execution by predeclaring its read-set and write-set. ... Conservative 2-PL is Deadlock free and but it does not ensure a Strict schedule(More about this here!).

Is rigorous 2PL deadlock free?

yes conservative 2PL is recoverable, serializable,deadlock free but still it suffers from starvation.

Can deadlocks occur in strict 2PL?

Rigorous 2PL :

There is no deadlock . Also, a younger transaction requesting an item held by an older transaction is aborted and restart with the same timestamp, starvation is avoided.

What is 2PL strict locking?

Strict-2PL holds all the locks until the commit point and releases all the locks at a time . Strict-2PL does not have cascading abort as 2PL does.

Which 2PL is deadlock free?

Conservative 2PL is deadlock free,but Strict 2PL can have deadlock.

Why is strict 2PL popular?

Strict 2PL is popular for many reasons. One reason is that it ensures only ‘safe’ interleaving of transactions so that transactions are recoverable , avoid cascading aborts, etc. Another reason is that strict 2PL is very simple and easy to implement.

How does strict 2PL rule work?

Strict Two-phase locking (Strict-2PL)

The only difference between 2PL and strict 2PL is that Strict-2PL does not release a lock after using it . Strict-2PL waits until the whole transaction to commit, and then it releases all the locks at a time. Strict-2PL protocol does not have shrinking phase of lock release.

What is growing and shrinking phase?

Growing Phase: New locks on data items may be acquired but none can be released . Shrinking Phase: Existing locks may be released but no new locks can be acquired.

How can we avoid deadlock in DBMS?

A deadlock can be prevented if the resources are allocated in such a way that deadlock never occurs . The DBMS analyzes the operations whether they can create a deadlock situation or not, If they do, that transaction is never allowed to be executed.

What are the four conditions needed for a deadlock to occur?

mutual exclusion: at least one process must be held in a non-sharable mode.
hold and wait: there must be a process holding one resource and waiting for another.
No preemption: resources cannot be preempted.
circular wait: there must exist a set of processes.

How can deadlock be avoided when using 2PL?

Deadlocks may happen under 2PL, when two or more transactions have got a lock and are waiting for another lock currently held by one of the other transactions. Deadlock cannot be avoided , but can be detected (cycle in wait graph). At least one of the participating transactions needs to be aborted by the DBMS.

Which lock is used to write an DB object?

DB applications support both exclusive and non-exclusive locks . Exclusive locks are granted when a locker wants to write to an object. For this reason, exclusive locks are also sometimes called write locks. An exclusive lock prevents any other locker from obtaining any sort of a lock on the object.

What is a 2PL?

A 2PL is an asset-based carrier that is responsible for the method of transportation . Examples of 2PLs include shipping lines which operate the ships, airlines that operate the planes and haulage companies that operate vehicles.

What are the advantages of strict two phase locking?

Answer: Rigorous two-phase locking has the advantages of strict 2PL. In addi- tion it has the property that for two conflicting transactions , their commit order is their serializability order. In some systems users might expect this behavior.

What is 2 phase locking protocol?

Two Phase Locking Protocol also known as 2PL protocol is a method of concurrency control in DBMS that ensures serializability by applying a lock to the transaction data which blocks other transactions to access the same data simultaneously. Two Phase Locking protocol helps to eliminate the concurrency problem in DBMS.