Contents
- 1 Is the least restrictive of the transaction isolation levels?
- 2 Which transaction isolation level is the most restrictive?
- 3 What is the least restrictive isolation level that will prevent phantom reads?
- 4 Which is better transaction isolation or performance in Oracle?
- 5 What does complete isolation of concurrently running transactions mean?
Is the least restrictive of the transaction isolation levels?
The least restrictive of the transaction isolation levels is read uncommitted. When using this option, a transaction may read information that has been changed by other, uncommitted transactions. It means that it is possible to encounter dirty reads, non-repeatable reads and phantom reads.
Which level of transaction isolation provides the greatest degree of isolation among concurrently executing transactions?
Serializable – This is the Highest isolation level. A serializable execution is guaranteed to be serializable. Serializable execution is defined to be an execution of operations in which concurrently executing transactions appears to be serially executing.
Which transaction isolation level is the most restrictive?
The range locks are held until the transaction completes. This is the most restrictive of the isolation levels because it locks entire ranges of keys and holds the locks until the transaction completes. Because concurrency is lower, use this option only when necessary.
What concurrent processing problem occurs when a transaction rereads data and finds new rows that were inserted by a different transaction since the prior Read group of answer choices?
A dirty read is a problem with concurrent processing when a transaction rereads data it has already read and finds modifications or deletions caused by another transaction. One way to prevent concurrent processing problems is to lock data that are retrieved for update.
What is the least restrictive isolation level that will prevent phantom reads?
25 Cards in this Set
| The recovery technique in which the database is returned to a known state and then all valid transactions are reapplied to the database is known as: | rollforward. |
|---|---|
| What is the least restrictive isolation level that will prevent phantom read problems? | Serializable. |
Which is isolation level provides complete isolation from concurrency effects?
The only transaction isolation level that provides complete isolation from concurrency effects is serializable. The SQL Server implementation of the serializable isolation level means a transaction will see the latest committed data, as of the moment that the data was first locked for access.
Which is better transaction isolation or performance in Oracle?
In short, real-world considerations usually require a compromise between perfect transaction isolation and performance. Oracle offers two isolation levels, providing application developers with operational modes that preserve consistency and provide high performance.
Is there isolation level that reads only committed data?
Both those isolation levels are guaranteed to read only committed data, yet we obtained a result that represents no committed state of the database! The only transaction isolation level that provides complete isolation from concurrency effects is serializable.
What does complete isolation of concurrently running transactions mean?
Complete isolation of concurrently running transactions could mean that one transaction cannot perform an insert into a table being queried by another transaction. In short, real-world considerations usually require a compromise between perfect transaction isolation and performance.