Before you examine the cause of the problem in more detail, perform these preliminary checks. These might highlight a simple cause or, at least, narrow the range of possible causes.
As you go through the questions, make a note of anything that might be relevant to the problem. Even if the observations you record do not at first suggest a cause, they could be useful to you later if you need to carry out systematic problem determination.
If the system has not run successfully before, it might not have been installed or configured correctly. You can check that CICS® Transaction Gateway installed correctly by running one of the sample programs; for more information, see Using the sample programs to check your configuration. You can also use the JCA resource adapter installation verification test (IVT) to test that the connection from WebSphere® Application Server through CICS Transaction Gateway to CICS Transaction Server is working correctly.
If you are currently upgrading CICS Transaction Gateway, ensure that you are aware of all the changes that have been made for this release, and make sure you have made any necessary configuration changes. For more information, see Upgrading.
CICS Transaction Gateway writes information, warning and error messages to the message logs (for more information, see General information about messages). Information messages allow you to check that your system is working correctly; warning and error messages inform you about problems. If warning or error messages were produced when CICS Transaction Gateway started, or while the system was running, these might indicate the cause of the problem.
If you have installed new versions of software components, or a new or modified application, check for warning and error messages. Consider backing out the changes and see if the problem still occurs.
If you have changed your CICS TG configuration or changed any CICS resources check that the changes have not caused any warning or error messages. Also check the configuration of the client application. For more information, see Configuring.
If you have applied a PTF, check that it installed successfully and that you did not receive any warning or error messages during installation. Also consider any service changes that have been applied to other programs, which might affect CICS Transaction Gateway.
Review the documentation that was supplied with the PTF to ensure that the instructions were followed correctly. If the PTF was installed correctly, try uninstalling it and see if the problem still occurs.
If you can identify a client application that is always in the system when the problem occurs, check it for coding errors. If the client application has not yet run successfully, examine it carefully to see if you can find any errors. If you have made changes to the client application since it last ran successfully, examine the new or modified part of the application. Consider the functions of the client application that might not have been fully exercised before.
If the problem seems to be related to system loading, the system might be running near its maximum capacity, or it might be in need of tuning. Check that you have defined sufficient resources (for example, connection manager threads and worker threads). Typically, if you had not defined sufficient resources, you might find that the problem is related to the number of users of the application.
If the problem occurs at specific times of day, it could be dependent on system loading. Typically, peak system loading is at mid-morning and mid-afternoon, so those are the times when load-dependent problems are most likely to happen. Use the CICS TG interval statistics to determine when peak loading occurs and the resource usage at the time; for more information, see Statistics.
Regular backup jobs or other system maintenance might also cause unexpected problems at specific times of day.