Hi Sanjay,
Is there any compression enabled for the table? What is the value of
compress_fot in dba_tables??
Regards,
RRA
On Sat, May 18, 2019, 03:58 Mark W. Farnham <mwf@xxxxxxxx> wrote:
A quick sanity check is if append is “fast” for one row and conventional
is “slow” for one row, then you have one of several possible problems that
can involve the ASSM free bitmap finding a block to shove something into.
This is sometime associated with an “empty front” problem which can be
identified by selecting a non-indexed column from the table where rownum <
2, and observing that your session stats read many blocks to get the first
row.
Your mileage may vary. A really horrible result may indicate that that
fastest path to a solution is a rebuild of a partition or table, but please
don’t get on a treadmill of rebuilding things that don’t need to be rebuilt.
mwf
*From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Sanjay Mishra (Redacted
sender "smishra_97" for DMARC)
*Sent:* Friday, May 17, 2019 5:32 PM
*To:* dmarc-noreply@xxxxxxxxxxxxx; Andy Sayer
*Cc:* Oracle-L Freelists
*Subject:* Re: Simple Insert - very slow
Andy
Thanks for the update. Based on the Obj Id with trace on the Insert
process, it is Table itself reported. This table is recently exported and
imported and Index was only created less than a month back. Surprisingly
not able to understand as to why it is doing cell single block physical
read to the table. I will also check your link and do more troubleshooting
Tx
Sanjay
On Friday, May 17, 2019, 10:29:45 AM PDT, Andy Sayer <andysayer@xxxxxxxxx>
wrote:
First step would be to see which object is responsible for all the IO, in
my experience it’s usually down to one index.
Have a look at
https://ctandrewsayer.wordpress.com/2017/02/16/not-all-indexes-are-created-equally/
for how I’ve tackled this before.
It might be you’ve got a “bad index” or it might be that you’ve got an
okay index that turned “bad”.
We had a case where an index exploded and was purely ITL for the first few
thousands leaf blocks, we reset the sequence (told to by support) which
meant that all our inserts had to scan those few thousand leaf blocks to
insert one row.
First step is identifying the object
Andy
On Fri, 17 May 2019 at 16:47, Sanjay Mishra <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Hi All
We have a table with around a billion rows with one Primary Key. Number of
columns in the table are fewer than 10 and all are numbers data type.
Application is doing few million inserts but running very slow. It is
Exadata with two node and 10CPU and good SGA (bufer Cache 10G). Waits are
coming heavily only for "cell single block physical read" for Insert
process. While doing SQL Monitor shows it is doing high IO like more than
100G for simple Insert. Oracle version is 12.2.
Any suggestions as what can be the reason for this wait event in this
scenario.
TIA
Sanjay
