What is cursor stability

pankajupadhyay · New User Joined: 04 May 2007 Posts: 13 Location: pune

HELLO,
could u plz tell me what is cursor stability
i am confuse in isolation levels and acquire/release

shane · Posted: Wed May 23, 2007 12:01 am

Hi,

First go through your text book before putting the question here.

prasadvrk · Posted: Wed May 23, 2007 12:03 pm

Here is an excerpt from IBM bulletin for your understanding.

Cursor Stability

Cursor Stability (CS) locks any row accessed by a transaction of an application while the cursor is positioned on the row. This lock remains in effect until the next row is fetched or the transaction is terminated. However, if any data on a row is changed, the lock must be held until the change is committed to the database.

No other applications can update or delete a row that a Cursor Stability application has retrieved while any updatable cursor is positioned on the row. Cursor Stability applications cannot see uncommitted changes of other applications.

Recalling the example of scanning 10 000 rows, if you use Cursor Stability, you will only have a lock on the row under your current cursor position. The lock is removed when you move off that row (unless you update that row).

With Cursor Stability, both nonrepeatable read and the phantom read phenomenon are possible. Cursor Stability is the default isolation level and should be used when you want the maximum concurrency while seeing only committed rows from other applications.