Sessions are waiting on buffer busy wait with P3 value 130 in v$s

From: Srikannan Gopalsamy <sgopalsamy_at_walmart.com>
Date: Thu, 24 May 2001 15:19:17 -0700
Message-ID: <F001.0030E552.20010524152549@fatcity.com>

We've lot buffer busy waits in data block with P3 value 130 in V$session.

I've read about this in few notes, but still I do not understand few things.

P3=130 means:

---

Block is being read by another session and no other suitable block image was found, so we wait until the read is completed. This may also occur after a buffer cache assumed deadlock. The kernel can't get a buffer in a certain amount of time and assumes a deadlock. Therefore it will read the CR version of the block.

Does it mean that the block is being held in an incompatible mode by the first session or set of sessions reading it in shared mode, and current session is trying to lock it exclusively for a DML and waiting for the same.

What are steps we can take to avoid this types of buffer busy waits?

Thanks for your help.
Sri
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Author: Srikannan Gopalsamy
  INET: sgopalsamy_at_walmart.com

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