Difference between the KEEP BUFFER and default BUFFER

[jcote]

Here is the definition of the KEEP BUFFER:
"A keep pool is used for storing buffers for database objects you definitely want to have persist in your buffer cache. Objects in the keep pool will not be eliminated from memory."
This definition comes from an Oracle Book (Certification guide for 8.0) in the chapters regarding the 8i features.

What is the difference between that, and the default Buffer pool?

 

[jimbopalmer]

normally statements age out if they are not used, so the ppol does not run out of memory The one thing you can't give for your heart's desire is your heart. - Lois McMaster Bujold

 

[carp]

Well, two things here:

1. The book is a little misleading - if you have 5M designated for your KEEP pool, fill it with objects, then try to add more objects, some of the objects in the KEEP pool will be overwritten, just like the DEFAULT pool.

2. Unlike the DEFAULT pool, only objects earmarked for the KEEP pool are loaded into the KEEP pool. Good candidates for the KEEP pool are lookup tables that you want to keep cached. Other tables can go compete for buffers in the DEFAULT pool. This is why you find general directives for sizing the KEEP pool that look like "estimate the total size of ALL tables you want to load into the KEEP pool and add 10 percent", etc.

Essentially, KEEP and DEFAULT work the same way - it's just that you can specify which tables can get into the KEEP pool.

 

[jcote]

Thank you.