Re: 'write complete waits' with unknown SQLID?

I think David is correct for my case - Oracle is reading before images and writing updates for the LOB.
This was a "large" insert, however, after reading some more and refreshing my memory, inserts on LOBs operate in the same way as updates (rollback for LOBs is internal to the LOB segment). The single session was a foreground session.
(I haven't watched a "large" insert into a LOB for quite a few versions)

On Mon, Mar 10, 2014 at 5:23 PM, Stojan Veselinovski < stojan.veselinovski_at_gmail.com> wrote:

> Funnily enough I've just seen as similar thing but mine was across a whole
> host of sessions once I killed a data pump job that was running too slow.
>
> Could be related to a large transaction rollback.
>
>
> On Tue, Mar 11, 2014 at 9:52 AM, David Fitzjarrell <oratune_at_yahoo.com>wrote:
>
>> LOB writes are a bit different from 'standard' writes (read that as
>> 'non-LOB'). Before images of LOB data are stored in the LOB itself, and
>> Oracle reserves PCTVERSION of the LOB storage for LOB before images. The
>> PCTVERSION setting reserves that percentage of the total number of chunks
>> of LOB data which have been allocated during the update process. I expect
>> that these 'write complete waits' are because Oracle is updating a LOB and
>> is reading before images from the LOB and writing updates to the LOB. This
>> may be happening after the active update has completed (I believe we could
>> consider this 'background processing' for the LOB) which may be why there
>> is no SQL_ID available.
>>
>> My two cents.
>>
>>
>> David Fitzjarrell
>> Primary author, "Oracle Exadata Survival Guide"
>>
>>
>> On Monday, March 10, 2014 4:29 PM, Rich <richa03_at_gmail.com> wrote:
>> Hi List,
>> Oracle 11.2.0.3 on RHEL 6.3 w/ASM.
>>
>> We see 'write complete waits' from a single session with no SQLID from
>> OEM...
>>
>> I see the definition for this wait is at
>> http://docs.oracle.com/cd/B16240_01/doc/doc.102/e16282/oracle_database_help/oracle_database_wait_bottlenecks_write_complete_waits_pct.html(at least for 10.2 - I don't see any Oracle documentation on this in the
>> 11.2 set).
>>
>> Looking at v$session, I see that the file# is a file in a TS which only
>> has a [securefile] LOB.
>>
>> How do we determine what is happening with this session and why?
>>
>> TIA,
>> Rich
>>
>>
>>
>
>
> --
> Stojan
> www.stojanveselinovski.com/blog
> www.stojanveselinovski.com
>

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