RyanJames

 Profile Answers by RyanJames Questions by RyanJames

• May 2nd, 2007

 

In some circumstances, the database server can bypass the overhead of the buffer pool when it performs a sequential scan. Such a sequential scan is termed a light scan.Light scans can be used only for sequential scans of large data tables and are the fastest means for performing these scans. System catalog tables, tables smaller than the size of the buffer pool, and tables containing varchar data do not use light scans.

Bessie

 Profile Answers by Bessie Questions by Bessie

• May 2nd, 2007

 

Light scans occur under the following conditions: The optimizer chooses a sequential scan of the table. The number of pages in the table is greater than the number of buffers in the buffer pool. The isolation level obtains no lock or a shared lock on the table: Dirty Read (including non logging databases) isolation level Repeatable Read isolation level if the table has a shared or exclusive lock
Committed Read isolation if the table has a shared lock