JCO - Model Data Destination connection is broken from time to time

Question

Hi, SDN Fellows.
I have set up both JCO Modeldata Destination and RFC Metadata Destination. For Modeldata Destination, I set up as Message Server.
JCo Pool Configuration
Maximal Pool Size :  5
Maximum Connections: 10 
Connection Timeout (msec.): 10 
Maximum Waiting Time (msec.): 30
Logon Group: Public
User Authentication: Ticket
SNC: OFF
I set up my RFC Metadata Dest as Application Server, User Authetication: Userid/Password.
(This configuration is suggested by a lot SDN experienced fellows as best practice)
From time to time, I am getting this error when I run my Web Dynpro application in the portal.
<i>Could not create JCOClientConnection for logical System: XXX_WD_MODELDATA_DEST - Model: class com.lenovo.model.locid.ZIBP_RFC_GET_LOCIDS. Please assure that you have configured the RFC connections and/or logical system name properly for this model!</i>
Sometimes, I have to increase the JCo Pool Configuration: like
Maximal Pool Size :  5 to 20
Maximum Connections: 10  to 50
Connection Timeout (msec.): 10  to 50
Maximum Waiting Time (msec.): 30 to 60
to solve the problem.
Sometimes, I need to restart the server node to "clear the JCO caches and the running JCO instances.
From the WDJ development, I have combined all the 10-12 adaptive JCO MODELs to one MODEL to reduce the JCO connections.
But I still not able to nail down the actual cause of the problems.
I am currently in the Dev environment with less users. I am just worry that things get worse if we move to Prod which have higher users activities on the WDJ application.
Please advise what I should do to solve this problem. 
Thanks.
Kent

Answer 1

Hi Kent,
you can do two steps here:
1. If you havent already done so - please close the model connection from your code after execution of each BAPI. Close the connection with code like below:
wdContext.<your model element>().modelObject().modelInstance().disconnectIfAlive();
this will ensure that there is no hanging connection even for a single moment.
2: Go though the documents am listing below. We need to understand these JCo destination's connection pool settings. Increasing the connection pool numbers without understanding will increase the problem rather decreasing it.
See
<a href="https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/library/webdynpro/wd%20java/guertler/how%20to%20configure%20the%20jco%20destination%20settings.pdf">THIS</a> Help file here. An excellent one.
Also see
<a href="https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/11c3b051-0401-0010-fe9a-9eabd9c216de">RFC DOs & DONTs</a>
First link I provided should be immensely helpful in calculating the connection numbers for your application. But it has to be calculated by you only as other wont understand your application and its usage better than you.
Hope it helps!!!
Shubhadip