FAQs(346 to 360)

Q246) What is an asychronous write?

A246) It is a write to disk that may occur before or long after a commit. The write is controlled by the buffer manager.

Q247) What is a lock?

A247) A lock is the mechanism that controls access to data pages and tablespaces.

Q248) What is meant by isolation level?

A248) This is a key concept for any relational database. Isolation level is the manner in which locks are applied and released during a transaction. For DB@ a 'repeatable read' holds all locks untile the transaction completes or a syncpoint is issued. For transactions using 'cursor stability' the page lock releases are issued as the cursor 'moves', i.e. as the transaction releases addressability to the records.

Q249) What are leaf pages?

A249) They are the opposite of root pages. Leaf pages are the lowest level index pages - the pages that contain index entries and information to the corresponding table rows.