Troubleshoot MES transactions

Troubleshoot the following specific issues with MES transactions:

Result of an MES XML command activity execution error

When the execution of an MES XML Command activity that is in a workflow that includes MES transaction control activities results in an error, the transaction is automatically rolled back. This is true regardless of whether the activity that results in an error is participating in a transaction or not.

Blocked transactions

Some transactions might be blocked or might not work properly if the stored procedures involved in the transaction are missing NOLOCK hints. As a result, the transaction might not complete within the transaction timeout period, which will cause changed data to be rolled back.

If using custom stored procedures, make sure NOLOCK hints are added to the SQL SELECT statements to prevent transactions from being blocked.

It is recommended to not use any activities inside a transaction that require human intervention to control the flow. It is also recommended to not use activities that take long to complete.

MES error variable configuration

Extract workflow execution error information

There are two MES error variables that can be used to extract the error information (if any) during the workflow execution.

• MES_Error_Desc: If an error occurs during the workflow execution, this variable will be updated with the error. The last error from the workflow execution will be updated in this variable. In case of an error, this variable will be automatically created by the MES activities and the error message is persisted on this variable.

• ^MES_Error_Desc_ActivityName: You can create this variable on the Start activity and configure it for a specific activity, where ActivityName is the name of the activity. This variable is updated with the error message from the activity if any error occurs within that activity. This will help the client applications to extract any error (if any) from a specific activity. Note that a variable of this type will not be created during workflow execution. However, if any such variable was created ahead of time, then the error message (if any) will be updated on this variable.

Note that variable names are case-sensitive.

Following is a list of internal variables that are not to be used in activities:

• MES Authenticated User

• MES Session Identifier

• MES Transaction ID

Configure a blocking output activity to reference design-time MES variables

The following design-time MES variables can be referenced in a workflow through the Blocking Output activity. However, the other MES variables cannot be used with a Blocking Output activity as they are inactive.

You can set variables for the Blocking Output by selecting their corresponding Variable.SubmittedBy.MES options in the Variable field type list to build a custom message.

Log client transactions

If the LogClientTransactions flag in the Operations Control Management Console (shown below) is turned on for the MES middleware, transaction information—such as when the transaction started, the transaction ID, and the XML commands participating in the transaction—will appear in the Log Viewer.