What are the types of locking protocols that MySQL uses for locking data items?
At the table level, there are five different types of locks:
- Exclusive (X)
- Shared (S)
- Intent exclusive (IX)
- Intent shared (IS)
- Shared with intent exclusive (SIX)
What are the locking techniques for concurrency control?
These are briefly explained below.
- Two-Phase Locking Protocol: Locking is an operation which secures: permission to read, OR permission to write a data item.
- Time Stamp Ordering Protocol:
- Multiversion Concurrency Control:
- Validation Concurrency Control:
What is concurrency control locking?
Shared locks can be shared between multiple transactions as there is no data being altered. Exclusive locks are used when write operation is performed. Only the transaction holding the exclusive lock is allowed to make changes to the data value.
What is locking in MySQL?
A lock is a mechanism associated with a table used to restrict the unauthorized access of the data in a table. MySQL allows a client session to acquire a table lock explicitly to cooperate with other sessions to access the table’s data.
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.
What are concurrency control protocols?
The concurrency control protocols ensure the atomicity, consistency, isolation, durability and serializability of the concurrent execution of the database transactions. Therefore, these protocols are categorized as: Lock Based Concurrency Control Protocol. Time Stamp Concurrency Control Protocol.
How do locks work in MySQL?
InnoDB implements standard row-level locking where there are two types of locks, shared ( S ) locks and exclusive ( X ) locks.
- A shared ( S ) lock permits the transaction that holds the lock to read a row.
- An exclusive ( X ) lock permits the transaction that holds the lock to update or delete a row.
Does MySQL have row locking?
If the tables use InnoDB, MySQL automatically uses row level locking so that multiple transactions can use same table simultaneously for read and write, without making each other wait.
What is CCP concurrency control protocols?
The concurrency control protocols ensure the atomicity, consistency, isolation, durability and serializability of the concurrent execution of the database transactions. Lock Based Concurrency Control Protocol. Time Stamp Concurrency Control Protocol.
What is the advantage of 2PL?
The obvious advantage of strict 2PL over rigorous 2PL is that it increases concurrency on each site, by allowing transactions to access the objects, read unlocked by Ti, without having to wait Ti’s termination.
What is the difference between exclusive lock and shared lock?
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 the use of lock table query control concurrency?
Table Locks (TM) Table-level locks are primarily used to do concurrency control with concurrent DDL operations, such as preventing a table from being dropped in the middle of a DML operation. When a DDL or DML statement is on a table, a table lock is acquired. Table locks do not affect concurrency of DML operations.