Jack,
When you say "/spending a lot of time/", do you mean a lot of
executions, or each execution averaging a lot of time?
Are you seeing this looking at AWR/ASH or extended 10046 event trace files?
Depending on the age of the Exadata or the workload, "cell single block
physical read" usually averages no more that 0.5 milli-seconds,
frequently less. I'd be surprised if the average wait was over 1 ms.
If you're tracking the expdp sessions or monitoring using V$ASH, can you
capture what P1 (i.e. file#) and P2 (i.e. block#)? P3 should be "1" for
single-block reads, of course.
If the expdp is hitting a lot of small tables, or tables with lots of
small partitions or subpartitions of only a few blocks, then that's one
reason single block reads might be prevalent. Is table compression
involved? That's why it would be good to capture P1 and P2 from V$ASH
or 10046 and translate it to an object name using DBA_EXTENTS.
Hope this helps...
-Tim
On 12/15/2021 6:58 PM, Jack van Zanen wrote:
Hi
Oracle 12.2.0.1 Exadata
I am running a datapump and two of the workers are spending a lot of time on
- cell single block physical read
- cell single block read request
This does not make sense to me as it is full expdp I would expected a full table scan type of wait, not single block
I checked mos but my search did not find anything related to my version
Does anyone know of any reason why this might happen?
Jack van Zanen
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