System logger is a set of services that allows an application to write, browse, and delete log data. You can use system logger services to merge data from multiple instances of an application, including merging data from different systems across a sysplex.
For
example, suppose you are concurrently running multiple instances
of an application in a sysplex, and each application instance can
update a common database. It is important for your installation to
maintain a common log of all updates to the database from across the
sysplex, so that if the database should be damaged, it can be restored
from the backup copy. You can merge the log data from applications
across the sysplex into
a log stream, which
is simply a collection of data in log blocks residing
in the coupling facility and on DASD (see Figure 1).
Figure 1. System Logger
Log Stream