According to the two-phase locking protocol, a
transaction handles its locks in two distinct, consecutive phases during the transaction's execution
: Expanding phase (aka Growing phase): locks are acquired and no locks are released (the number of locks can only increase).
Which of the following are phases of 2 phase locking protocol?
The two phase locking protocol consists which of the following phases? Explanation: The two phased locking protocol consists of
the growing phase and the shrinking phase
. Explanation: If a transaction may obtain locks but may not release any locks then it is in growing phase.
What is the two-phase locking protocol?
A transaction is said to follow the Two-Phase Locking protocol if
Locking and Unlocking can be done in two phases
. 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.
What is 2 phase locking protocol 2PL )? Describe with the help of an example?
The two-phase locking protocol
divides the execution phase of the transaction into three parts
. In the first part, when the execution of the transaction starts, it seeks permission for the lock it requires. In the second part, the transaction acquires all the locks.
Is 2 phase locking serializable?
In 2-phase locking protocol – all locks are held until the transaction commits or aborts. Strict 2-phase locking protocol ensures
both a serializable schedule
and one that avoids cascading aborts.
What is the purpose of two-phase locking?
In databases and transaction processing, two-phase locking (2PL) is
a concurrency control method that guarantees serializability
. It is also the name of the resulting set of database transaction schedules (histories).
What is strict two-phase locking?
Strict Two-Phase 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.
What is two phase locking describe with example?
Two-Phase Locking (2PL) is
a concurrency control method which divides the execution phase of a transaction into three parts
. It ensures conflict serializable schedules. If read and write operations introduce the first unlock operation in the transaction, then it is said to be Two-Phase Locking Protocol.
What is locking protocol in DBMS?
Locking protocols are used in database management systems as
a means of concurrency control
. Multiple transactions may request a lock on a data item simultaneously. Hence, we require a mechanism to manage the locking requests made by transactions. Such a mechanism is called as Lock Manager.
Does two phase locking protocol ensure conflict serializability?
This is a protocol which ensures conflict-serializable schedules.
The protocol assures serializability
. It can be proven that the transactions can be serialized in the order of their lock points (i.e., the point where a transaction acquired its final lock). Two-phase locking does not ensure freedom from deadlocks.
What benefit does strict two phase locking provide?
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.
Shared lock can be placed on objects that do not have an exclusive lock already placed on them. Exclusive lock can only be placed on objects that do no have any other kind of lock. … Any number of transaction can hold shared lock on an item.
Exclusive lock can be hold by only one transaction
.
What is two phase locking and how we can prevent deadlock?
Two phase locking prevents
deadlock from occuring in distributed systems by releasing all the resources it has acquired
, if it is not possible to obtain all the resources required without waiting for another process to finish using a lock. … This means that deadlock cannot occur due to resource contention.
How does two phase locking protocol ensure serializability explain?
Two 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
. … Instead, it only releases the acquired locks.
How does locking protocol work?
When a locking protocol is being used,
a lock held by one transaction can block a lock request from another transaction
. If there are no circular waits for a lock, then the lock will ultimately be granted. If there are circular waits, then deadlock occurs.
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.
