Locking is a mechanism to ensure data integrity while allowing maximum concurrent access to data. It is used to implement concurrency control when multiple users access table to manipulate its data at the same time.
What is the advantage of locking Mcq?
Online Test
| 3. | The advantage of optimistic locking is that: |
|---|---|
| a. | the lock is obtained only after the transaction has processed. |
| b. | the lock is obtained before the transaction has processed. |
| c. | the lock never needs to be obtained. |
| d. | transactions that are best suited are those with a lot of activity. |
What is the disadvantage of locking in DBMS?
Here are some of their disadvantages: Table locking still allows multiple processes to read from a table at the same time, but if a process wants to write to a table, it must first get exclusive access, meaning it might have to wait for other sessions to finish with the table first.
What is locking explain types of locking?
Lock-based Protocols. Binary Locks ? A lock on a data item can be in two states; it is either locked or unlocked. Shared/exclusive ? This type of locking mechanism differentiates the locks based on their uses. If a lock is acquired on a data item to perform a write operation, it is an exclusive lock.
What is the disadvantages of locking Mcq?
Answer: Locking has a poor degree of concurrency. It in fact has no concurrency at all.
What is the use of lock table query?
The LOCK TABLE statement allows you to explicitly acquire a shared or exclusive table lock on the specified table. The table lock lasts until the end of the current transaction. To lock a table, you must either be the database owner or the table owner.
What is the advantage of locking in DBMS?
Locking is a mechanism to ensure data integrity while allowing maximum concurrent access to data. It is used to implement concurrency control when multiple users access table to manipulate its data at the same time.
What is the disadvantage of locking *?
Locking has a few other disadvantages. When a thread is waiting for a lock, it cannot do anything else.If a thread holding a lock is permanently blocked (due to an infinite loop, deadlock, livelock, or other liveness failure), any threads waiting for that lock can never make progress.
What is advantage of 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 are the two types of locks?
There are two types of lock:
- Shared lock: It is also known as a Read-only lock. In a shared lock, the data item can only read by the transaction.
- Exclusive lock: In the exclusive lock, the data item can be both reads as well as written by the transaction.
What is a database lock?
The process of locking a clinical trial database is an action taken to prevent further changes to the database.Once the database is complete and clean the database is locked to prevent further changes to the data and the analysis may be performed.
What is two phase locking with example?
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).
Strong strict two-phase locking.
| Lock type | read-lock | write-lock |
|---|---|---|
| write-lock | X | X |
What is lock conversion?
Lock conversion occurs when a process accesses a data object on which it already holds a lock, and the access mode requires a more restrictive lock than the one already held.Some lock modes apply only to tables, others only to rows, blocks, or data partitions.
What are the advantages of concurrent execution of transaction over serial execution of transaction?
When executing serially, one long transaction is executing and a very small transaction may be on the queue for its turn. This increases the waiting time of small transaction. Hence, if we execute transactions simultaneously, the waiting time would be much reduced when compared to the serial execution.
Which level of locking provides the highest degree of?
Row is a kind of level locking that offer the highest degree of concurrency in the relational database.
What is lock in Oracle database?
How Oracle Locks Data. Locks are mechanisms that prevent destructive interaction between transactions accessing the same resourceeither user objects such as tables and rows or system objects not visible to users, such as shared data structures in memory and data dictionary rows.
What does flush tables with read lock do?
FLUSH TABLES WITH READ LOCK is useful if you want to take a backup of some tables. When FLUSH TABLES WITH READ LOCK returns, all write access to tables are blocked and all tables are marked as ‘properly closed’ on disk. The tables can still be used for read operations.
On which level we can apply the locks?
On which level we can apply the locks? Locking can be applied on either of these ? Page, table and table space.
What is locking mechanism Why is it necessary?
Locking mechanisms are a way for databases to produce sequential data output without the sequential steps. The locks provide a method for securing the data that is being used so no anomalies can occur like lost data or additional data that can be added because of the loss of a transaction.
What is lock point in DBMS?
The Lock Point is when all locks are held for the whole transaction. Binds all of the data used in a transaction together. It, therefore, prevents a transaction from being split into parts.
What is locking in SQL Server?
Locks are held on SQL Server resources, such as rows read or modified during a transaction, to prevent concurrent use of resources by different transactions. For example, if an exclusive (X) lock is held on a row within a table by a transaction, no other transaction can modify that row until the lock is released.
Contents