enque/statistics_file is a SAP Parameter attribute which is used to control Statistics file for Enqueue (full path) 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 .
Enqueue statistics file (full path).
You can display the file in SM12 by choosing Extras -> Statistics.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.