RE: [EXTERNAL] Re: enq: TS - contention (solved, or not?)

DELETE FROM AR_AUTOREM_INTERIM WHERE BATCH_ID = :B1   Thanks

From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of Mark W. Farnham Sent: Tuesday, November 14, 2023 12:09 PM To: jlewisoracle_at_gmail.com; oracle-l_at_freelists.org Subject: RE: [EXTERNAL] Re: enq: TS - contention (solved, or not?)  

IF they still use multiple logon names, multiple temporary tablespaces with different names from TEMP is another option (which could be nicely tuned for site load and job schedule if different users are in conflict.) Losing that trivial ability was a downside for running all jobs from “APPS.”  

IF this is a mixed EBS and other things database, then even if the EBS is a single logon name for job execution, either the EBS logon name (or all the other users, including folks who report on EBS things that use “TEMP” but are different from the logon for the jobs) can be moved to a different “TEMP.” Quite often lots of things use “TEMP” other than EBS, so this may be a useful thing even if it is only a bifurcation.  

IF there is a unified default logon name, then constructing multiple temporary tablespaces with all the appropriate grants is possible, but quite a hassle.  

I definitely like your idea of giving a tablespace group a try. Unless there are multiple logon names for the jobs, that is the least monkeying around. It might even be less monkeying around than different default temporary tablespaces with multiple logon names.  

As far as I know, they never implemented the enhancement request for “use ‘THIS’ tablespace as the temp for this session” and temporary tablespace groups was the “general” solution that quashed that user control oriented solution to this and similar contention (as well as direction to SSD, when SSD was usually a small portion of the available media farm.)  

Altering default temporary tablespace for a user, submitting a job immediately (which required keeping an open job slot), and then altering the default temporary tablespace back as another job also submitted to an open slot after a pause long enough for the first job to have used the altered temporary tablespace name) was a thing for a while that could make a big difference for critical jobs. This isn’t i/o rate, but that should also work for contention.  

I think I remember that correctly, but I’m not going to look it up. Oracle was never enthused about going to that level of engineering because it was anti-marketed as “complicated.”  

mwf  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jonathan Lewis Sent: Tuesday, November 14, 2023 10:20 AM To: oracle-l_at_freelists.org
Subject: Re: [EXTERNAL] Re: enq: TS - contention (solved, or not?)    

Mark, it seemed to be the Temp tablespace, so spreading objects is not an option. Since it seems to be a big file tablespace neither is adding more files - which might otherwise address the concurrency.

Using a tablespace group, though, might bypass the problem.    

Regards

Jonathan Lewis

(From my iPad mini; please excuse typos and auto-correct)    

On 14 Nov 2023, at 13:52, Mark W. Farnham <mwf_at_rsiz.com> wrote:



Just curious. Now that JL and others have documented the way to get the answer to your question, is your problem solved?  

Reminding that this is a contention issue (apparently not an i/o throughput problem), the trivial solution might be to un-dither objects from the tablespace evenly into multiple tablespaces based on totals of segments requested (and possibly released via truncate for some processes). It’s possible that some future patches and upgrades may require that you move the objects back to the default tablespaces.  

IF the occurrence of contention is periodic on a workday, weekly, monthly, quarterly, or annual basis, simply arranging in the scheduler to run the biggest allocators and de-allocators at times askew from each other.  

mwf  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Hameed Amir ("amir.hameed") Sent: Friday, November 10, 2023 1:47 PM
To: Jonathan Lewis
Cc: oracle-l_at_freelists.org
Subject: RE: [EXTERNAL] Re: enq: TS - contention  

Hi Jonathan,

Thank you for the explanation. I looked through DBA_HIST views for information on job A for periods when it finished successfully, and I found the following statement in all those periods:

DELETE FROM AR_AUTOREM_INTERIM WHERE BATCH_ID = :B1   It is a standard Oracle EBS table. It is partitioned and has no index on it.  

Can you please show me how to convert P2 into TS name below?  

Event = enq: TS – contention

P1 = 1414725635

P2= 196611

P3= 2  

Thank you,

Amir

From: Jonathan Lewis <jlewisoracle_at_gmail.com> Sent: Thursday, November 9, 2023 6:13 PM To: Hameed, Amir <amir.hameed_at_sleepnumber.com> Cc: oracle-l_at_freelists.org
Subject: [EXTERNAL] Re: enq: TS - contention  

CAUTION: External source  

I don't know all the options that might appear for the TS enqueue, but it is requested during the creation and dropping of many (probably all) types of segments. It's not restricted to temporary segments in the temporary tablespace.  

The p1, p2, p3 values for the event are

  name || mode, (0x5453000n) --- n is the mode, values 0 - 6

  con_id || ts#, (0xcccctttt) ,,, typical top 4 / bottom 4 hex characters, but the con_id might not be there

  tablespace relative block address   

If you can query v$lock id1 will be the (con_id || ts#) and id2 will be the block address.  

For creating a segment Oracle gets the TS lock once in exclusive mode on the segment header block. For dropping a segment Oracle gets the TS lock twice in exclusive mode, first for the segment header block, then for the first "data" block of the segment.    

It seems unlikely that the SQL you've shown would lead to any type segment creation - possibly in a RAC system and with a large number of PDBs, object types and users some feature of the view definition might cause a SYS-recursive query to generate a very bad plan with a huge temporary segment - but that would be a little surprising.  

Is there anything you know about procedures A and B that would lead to excessive numbers of segments being rapidly created and dropped, and possibly hitting some strange boundary conditions (e.g. lots being created - which take the TS enqueue - but the purge option not being specified on the drop - which would mean the TS enqueue wouldn't be taken, but a background might start dropping segments from the recyclebin when space pressure got too high). Another hypothetical problem could be excessive demand leading to automatic file extensions and an undetected deadlock.  

I think you need to work out what the procedures are doing around the time of the fail, and see if that gives you any clues. Perhaps you could be guided by the SQL_IDs in the ASH data in the couple of minutes leading up to the wait.    

Regards

Jonathan Lewis        

On Wed, 8 Nov 2023 at 18:02, Hameed Amir <dmarc-noreply_at_freelists.org> wrote:

Hi,

The database version is 19.17.0.0, running on OEL8.

In our Oracle E-Business Suite production database, a batch job (A) runs and spawns another job (B). Intermittently, job A runs longer and ends up getting terminated by the user. ASH data shows that the process running job A awaited the event "enq: TS - contention".  

Based on the limited information I have found, this event seems related to the TEMP tablespace. There is no SQL_ID associated with the session ID waiting on the event. There is a TOP_LEVEL_SQL_ID, which shows the following SQL statement:  

select directory_name from all_directories where directory_path = :1  

Has anyone run into this issue? Any feedback will be greatly appreciated.  

Thank you,

Amir