Re: Enqueue type - RO-Multiple Object Reuse (fast object reuse)

  • From: Riyaj Shamsudeen <rshamsud@xxxxxxxxxxxx>
  • To: kmoore@xxxxxxxxxxxx
  • Date: Wed, 31 Aug 2005 14:20:57 -0500

RO enqueue is acquired while dropping/truncating the objects. Drop /truncate will post the DBWR to flush the buffers associated with those objects. While DBWR is performing this operation, foreground process will wait for RO enqueue. Usually RO can be seen with CI (Cross Instance invalidation ) enqueues even in non-rac single instances

One of the primary reason is that DBWR is slow or buffer cache is too big.

What is surprising though, this behavior is very visible up to 9i. But, in 10g, drop will simply rename the objects ( for flashback feature). Clearing the recycle bin will take care of flushing the buffers and so this is not a bigger issue anymore. Did you disable the flashback feature by any chance ?

BTW, 10.0.3 looks too low of a version. So, far I have seen to be a stable release.


Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA (ver 7.0 - 9i)
Allocation & Assortment planning systems

Keith Moore wrote:

Does anyone have information on this?

We have setup a two node 10g RAC database, Oracle version 10.0.3.

I ran statspack for a test and this shows up as the top wait time in one
instance with 3 minutes of wait time during a 12 minute test.
Interestingly, it has less than one second of wait on the other instance.

Here is the statspack info:

Enqueue Type (Request Reason)
   Requests    Succ Gets Failed Gets       Waits Wt Time (s)  Av Wt Time(ms)
------------ ------------ ----------- ----------- ------------ --------------
RO-Multiple Object Reuse (fast object reuse)
      5,180        5,180           0       2,217          184          83.00
TX-Transaction (row lock contention)
         23           23           0          23            1          49.57

Any help would be greatly appreciated.



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