Datastage – Problem when running large parallel jobs

If you have large parallel jobs (8.1) running in Windows environment then it is worth checking the servers event log. You could find an error related to Nutcracker.exe. An administrator with access right on the server can see the events logs. 

Nutcracker error could come up while running very heavy jobs where total cpu utilization is upto or above 90% and server starts using virtual memory. This is just an example of the impact of running large parallel jobs in Windows server. Hence to make the system somewhat full proof following changes can be done in Windows registry. The idea is to tune the TCP/IP buffer, increase the heap size and set the virtual memory to the recommended amount.

To tune TCP/IP settings go to registry editor and check if MaxUserPort and TcpNumConnections keys are present in the TCP/IP buffer and connection registry. Generally they will not be there. TcpNumConnections settings will impact on number of Osh processes.

To change the settings 
Go to registry editor 
Go to HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > Services > Tcpip > Parameters.
Now on the right pane modify the values: 
Value Name: MaxUserPort
Value Type: DWORD
Value data: 65534
More information on MaxUserPort click here.

Value Name: TcpNumConnections 
Value Type: DWORD
Value data: 65534
More information on TcpNumConnections click here.

To change the heap size 
Go to registry editor and change the non interactive desktop heap size. 
Go to HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > Control > Session Manager > SubSystems.
Click on windows on the right pane. 
Now edit the ShareSection parameter in the value box 
Change the last value from 512 to 1024.

Now what is Desktop heap and why we are changing it? 

In windows anything you create as a desktop object has got some amount of memory attached to it which is known as single desktop heap. The desktop heap is responsible for storing user interface objects, for example menus (Start for example) and windows (any new Window). When we run any application which needs to create these kind of interface object it needs space (in general terms, however it does have a process by which it allocates the area.) which goes from Desktop heap. In normal scenarios no one bother about how much Desktop heap has been configured in the system. The interesting thing here is if the application does not require any kind of interface objects it will not allocate the area from heap. The value which we are changing here is related to non interactive desktop which is related to services. So we are allowing more heap size in our environment so that while running services it should not exhaust. If you need more information on Windows heap please click here.

Now the last bit is changing the virtual memory configuration.

Virtual memory can be configured by right clicking on “My Computer” and going to Advance tab’s performance section. Now change the virtual memory to the recommended size. For example if you have 8GB of RAM then recommended size would be 12 GB.

However all above setting can overcome issues related to large jobs but patches recommended for Nutcracker issue should also be installed.

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