FN_ASTAT is a SAP Parameter attribute which is used to control Application statistics filename 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 application statistic makes it possible to trigger statistic records
(regardless of rolls) from the application. These records are collected
in a separate file. The file name is defined using this parameter.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.