Skip to Main Content
Forums

Oracle Database Discussions

Announcement

For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle.com. Technical questions should be asked in the appropriate category. Thank you!

What does buffer pin mean?

ronald_2017Apr 20 2020 — edited Apr 20 2020

Hi All,

I am trying to learn the basic meaning of buffer pin? I just read the following thread and an article by Jonathan Lewis. For example, what is happening during full table scan without parallel hint? Before, multiblock read happen, does Oracle check for the buffer whether are they in buffer cache or not, right? I am just trying to investigate this process. However, there is noting about how these kinds of internals work. There are only one or two books on the market. And there is not enough information abot x$ tables such as x$bh etc. in oracle docs.

BUFFER IS PINNED COUNT

http://www.jlcomp.demon.co.uk/bbw.html 

  1. Calculate the hash bucket/chain id (using the tablespace, file, and block numbers, and block type).
  2. Grab the relevant cache buffers chains latch 
  3. Search the hash bucket/chain
  4. Pin the buffer header if found
  5. drop the latch
  6. Use the buffer (if it isn’t held by another session in an incompatible mode)
  7. Grab the latch
  8. Unpin the buffer header
  9. Drop the latch

Regards
Comments
Post Details
Added on Apr 20 2020
#general-database-discussions
2 comments
1,735 views