This topic does not apply to SAP systems running on IBM AS/400 and Microsoft Windows NT hosts. Central logging is not available on these platforms. See below for details on central logging with Windows NT systems.
You can configure your servers such that the system keeps a central log as well as logal logs. You need at least two SAP instances or application servers for central logging.One system is the central system. This collects the log data from the other instances or application servers.For central logging to work, you must:
· Set the logging parameters in each system profile
· Start a collection process on the central application server
· Start a sending process in the central system and in each instance.
A central log requires two processes - a sending process and a collection process.Each instance uses the sending process. It copies local messages from each instance into the central log.
The sending process is activated at regular intervals. When it is activated, it forwards all log messages that have been entered since the last time that it was activated. Once the local messages have been forwarded, the sending process becomes idle, to save system resources.
The intervals between activations of the send process can be less than one minute or more than 30 minutes. This is automatically dependent on the logging intensity of the application server. If a large number of log entries have been written since the last activation, the next interval is shortened accordingly.
The central instance uses a collection process as well as the sending process .The collection process collects the messages that have been sent by the send processes of the individual instances. The collection process is activated by communicatino requests from the send process.The collection process is idle between communication requests.
The send and collection processes both have a file using the extension pid. The pid file contains the operating system ID (process number) of the processor. If the pid file of a process contains the value -1, the process cannot run.If the pid file for a given process does not exist, the process has either not started or it has crashed.
The send process also has a file with the extension sta. The sta file contains the descriptor for the file that processe the send process. It also contains the byte offset that the process has already reached in the file.
The byte offset is not updated each time a log message is processed.
There is no central log in a Windows NT system. The processes that the central log uses are therefore not necessary.To suppress warning messages to do with the central log, set the SAP system parameter rslg/collect_daemon/host in your NT system to NONE.
Use the System log ® Choose ® All Remote System Logs function to read the data from all instances in your SAP system. If an alert occurs in the Alert Monitor, use Remote SysLog to analyze it.