Tuesday, July 16, 2013

Researching ADF 12c Connection Threshold Property Functionality

ADF 12c developer guide describes new ADF BC tuning property - Disconnect Application Module Upon Reaching Maximum Connection Threshold (jbo.ampool.connection_threshold). I was doing a bit of research around this property and testing how it works. It looks to me - it doesn't work yet, as it should. You should be careful using jbo.ampool.connection_threshold. As per developer guide, connection threshold functionality is enabled when threshold value is set to positive number. Once AM pool will grow more than this number, ADF BC will start disconnecting and releasing DB connections for the least used AM's. Disconnect will happen during AM pool cleanup, developer guide recommends to configure shorter pool cleanup interval (jbo.ampool.monitorsleepinterval). With normal ADF BC DB pooling enabled, disconnect will happen after each request. In theory connection threshold is supposed to optimize this and do disconnect only when exceeding configured threshold and during pool cleanup cycle. However this doesn't seem to work, at least based on my test.

My test was based on these tuning settings:


- Minimum Available Size changed to be 0, all AM instances will be cleaned

- Pool Pooling Interval changed to be 30 seconds. Meaning in 30 seconds interval AM pool cleanup monitor will wake up and try to disconnect AM instances exceeding connection threshold or inactive AM instances

- Idle Instance Timeout property is kept default 10 minutes on purpose, in order to force earlier disconnect from jbo.ampool.connection_threshold

- Disconnect Application Module Upon Release is not set. As it is stated in the developer guide, when positive threshold value is set - DB connection disconnect mode is set automatically (meaning no need to set it by yourself directly)

Connection threshold (jbo.ampool.connection_threshold) is set to be 3. Meaning when there will be more than 3 active AM's with DB connections, disconnect mechanism should start during next pool cleanup cycle:


I was running this test with 6 concurrent users, starting with the first user - completing first user actions and then starting with the next user. By the time 6th user starts his session, 30 seconds interval from the first user session was passed - pool monitor should disconnect exceeded number of connections - but this didn't happen. All 6 connections still remain reserved, with connection threshold set to 3 and pool monitor interval set to 30 seconds:


Here you can download sample application I was using for this test - ADFBCConnThresholdApp.zip. This tuning option looks to me very powerful for performance optimization and more optimal DB connection usage, hopefully it will be fixed soon and we could use it. Or may be my test was wrong, and it works already - let's see if we get more input regarding this tuning option.

19 comments:

Anonymous said...

And this is Oracle, I always wonder if it test its product before they release them.

Siu Fai Ng said...

Hi,

I am using 11.1.1.5 version. According to my understand, if there is no unreferenced AM instance, system will passivate and activate AM. If I set the Maximum Pool Size and Referenced Pool Size to a very very large value, the data control can always use the same AM for every HTTP request and no passivation is needed. The reason why I do not set the size to a very large value is that system will request operating system to allocate more memory and memory swap will occur. Swap is slower than passivation and that is the reason why we need to adjust the value. Right?

Andrejus Baranovskis said...

You should set referenced pool size to estimated number of concurrent users.

Andrejus

Siu Fai Ng said...

You assume that one user session will use only one instance of the AM, so set referenced pool size to estimated no of concurrent user. Right?
No matter the memory size of the server?

How about the Maximum Pool Size?

Andrejus Baranovskis said...

Yes, this is how is supposed to be.

Maximum pool size is usually irrelevant, it can be any high number.

Andrejus

Siu Fai Ng said...

Thanks for your help.

Besides AM configuration, do you suggest developer to create a shared AM which contains all the LOV of the system?

If yes, any benefit besides lessen data source connection? Say memory consumption? Is the improvement significant?

Tony

Andrejus Baranovskis said...

There is no need to include lov into am at all, lov are consumed from vo. Usually i dont see a need for shared am, as it is useless with adf shared libs.

Andrejus

Siu Fai Ng said...

I am using version 11.1.1.5 and trying to tune the performance.
According to the suggestion from the site ( http://www.oracle.com/technetwork/developer-tools/adf/learnmore/87-lov-using-shared-am-444769.pdf), they suggest to create a shared AM to minimize the data access from database. Do you suggest system to follow? If yes, will it improve the memory, database connection in version 11.1.1.5?

Thanks for your help in advance.

Tony

Andrejus Baranovskis said...

I think i already explained :)

Siu Fai Ng said...

Hi Andrejus,

For java class type DataControl/AM, does the system use the same java instance over several HTTP requests? If not, can I assume that the java instances are LOGICALLY the same? say the value of java attributes can carry forward to the next HTTP request.


Thanks,

Tony

Siu Fai Ng said...

Hi Andrejus,

Any relationship between Referenced Pool Size, Minimum Available Size and Maximum Available Size? Say Minimum < Referenced Pool Size < Maximum ?

If yes, any suggestion on the min and max value if referenced pool size is 1000?

Thanks.

Tony

Andrejus Baranovskis said...

It depends, I would need to test your application to answer properly.

Andrejus

Siu Fai Ng said...

Hi Andrejus,

Referenced pool size should be set to no of concurrent user. What do you mean concurrent user?
Assume the application has only one AM and 1000 users login the system . Around only 5% of users will submit the request at a particular moment. Should the referenced pool size be 1000? or 50?

In most application, it is no need to set "jbo.doconnectionpooling=true". Is it correct?

If we set jbo.doconnectionpooling to true, ADF will release the connection immediately after the HTTP request is completed and no need to wait for any monitoring task to clean up?

Thanks.

Tony

Andrejus Baranovskis said...

Hi,

Concurrent users - users working at the same time.

Not correct, I recommend to set "jbo.doconnectionpooling=true" almost in every application - this allows to clean statement cache in ADF and release memory.

Andrejus

Siu Fai Ng said...

Hi Andrejus,

Thanks for your prompt reply.
In my previous example, 1000 users login the system and submit requests to the system randomly. At a particular moment, maybe just 50 request. So concurrent user = 1000. right?

Andrejus Baranovskis said...

Hi,

No, this means 50 concurrent users.

Andrejus

Siu Fai Ng said...

Hi Andrejus,

There are 1000 users using the system in my example. For example, user01 - user50 insert a record to the view object but not yet committed. Then 10 seconds later, user51 - user100 insert a record to the view object without save. The 50 AM in the pool will passivate the data of user01-50 and serve user51 - user100. Is it correct?

If yes, there are 1000 users using the system and the AM will passivate frequently. It seems that setting the referenced pool size to 50, but not 1000 cannot prevent passivation. I do not why we need to set the referenced pool size to no of concurrent users, but not no of users using the system.

Appreciate for your prompt reply.

Thanks.

Regards,
Tony

Andrejus Baranovskis said...

I would need to come to your office or we could have conference call by remote to discuss it. This is quite complicate to give you precise answer through blog comment.

If you are interested - send me email.

Andrejus

Siu Fai Ng said...

Hi Andrejus,

Deeply appreciate your help and prompt reply.

I will send to your gmail account later.

Thanks again.

Tony