Question

____ isolation, where isolation can be READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ or SERIALIZABLE. The default is SERIALIZABLE.

1) READ UNCOMMITTED
2) READ COMMITTED
3) REPEATABLE READ
4) SERIALIZABLE

Answer 1

Isolation levels determine how transaction isolation is managed in databases. The four levels are READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, and SERIALIZABLE. The default level is SERIALIZABLE, which provides the strictest isolation ensuring serial execution of transactions.

Step-by-step explanation:

The isolation levels in the context of databases define how transaction isolation is handled. There are four main isolation levels:

• READ UNCOMMITTED: This level allows dirty reads. A transaction may see uncommitted changes made by another transaction, which risks reading data that might be rolled back.
• READ COMMITTED: This level prevents dirty reads. A transaction only sees committed changes made by other transactions, which provides a stable view of the database.
• REPEATABLE READ: This level ensures that if a transaction reads a record, subsequent reads will see the same data, even if another transaction modifies it.
• SERIALIZABLE: This is the highest isolation level. Transactions occur with complete isolation from one another, as if they were serialized.

The default isolation level as pointed out in the question is SERIALIZABLE. This is because SERIALIZABLE provides the strictest level of isolation, ensuring that transactions appear completely isolated and serial in their execution.