rsau/SQL-Audit/filename is a SAP Parameter attribute which is used to control Pattern for the Filenames of the SQL Audit information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
The template is used to create a file for the SQL audit. The target of
the search is a string of eight plus signs ("++++++++"). This string is
replaced by an eight-digit number (possibly with leading zeroes). In
addition, the parameter rsau/SQL-Audit/logdir is used to create the
complete file name.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.