Re: definition of "buffer is pinned count"

On Jun 7, 4:06 pm, wagen..._at_yahoo.com wrote:
> > BUFFER IS PINNED COUNT: Number of times a buffer was pinned when
> > visited. Reports the number of times Oracle visited a data buffer
> > without the expense of having to first use a latch.
>
> Oracle visited a data buffer without the expense of having to first
> use a latch
>
> How can oracle visit a data buffer without acquiring a latch? Please
> help me understand this or point me to any docs
>
> Thank you
> wagen

Google searches are quite helpful:
Keywords: without the expense of having to first use a latch

http://www.dizwell.com/prod/node/342
"The cost and effectiveness of buffer pinning can be seen in two statistics, buffer is pinned count which reports the number of times you have visited a buffer without the expense of having to use a latch; and no buffer to keep pinned count which should have been called 'no pin to pin a buffer with count' and tells you when you wanted to pin a buffer, but had either exceeded your limit, or could not find a free pin in the array."

Keywords: "BUFFER IS PINNED COUNT" Lewis

http://www.freelists.org/archives/oracle-l/06-2004/msg00697.html "Buffer is pinned count: -

    Oracle has previously pinned a buffer, and     not released it immediately. A pin may be     held for the duration of a database call.     Oracle can revisit the buffer by traversing     the pin without acquiring the latch, because     the presence of the pin ensures that no other     session could have acquired that buffer in a     conflicting fashion."

I believe that this topic is covered in "Cost-Based Oracle Fundamentals" as well.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Thu Jun 07 2007 - 15:28:44 CDT