Logging and Tracing in the VM
Container
Use
Logging and tracing are used to find the cause of any problems occurring within a program. There are different kinds of information and details for different user groups.
Users can look up in log files what the exact problem is. Administrators and developers can identify from the traces what the cause of the problem is and how it can be solved.
Features
The VMC logging and tracing system is called up by Java programs to output messages that enable errors to be found later and to reproduce the program flow. These Java programs can be components of the VMC environment itself, or even applications that use the VMC to execute Java code.
The Java program uses a log controller object created earlier to write the message. There are two types of log controllers.
● Categories to write the log messages These correspond to logical components such as /system/database, the parts of the name are separated by a forward slash (/).
● Locations to write traces for developers and administrators. The names of locations correspond normally to Java class names or packages, the parts of the name are separated by a point.
When you choose Log Administration → Log Display on the left-hand side, a new tree appears.
This contains the hierarchical structure for the locations. Beneath this the categories are listed.
Each message has a Severity level that together with the log controller setting determines whether the message is output or not. This allows you to restrict the number of messages to those of real interest.
Each log controller can enter separate settings. The path-like names of the log controllers enable them to be uniquely arranged in the tree, as settings are passed downwards in the tree. For instance, if a location is configured in such a way that it only outputs traces with a severity of at least WARNING, this is also valid for all the subordinate locations, unless these have their own settings.
Activities
You can view the log messages in the log administration in SM53, and you can also display and change the log settings.
The sections below contain more details:
Displaying and Changing Log Settings