Here are the few Remedy extensions that are used way back, I am trying to list all the new and changed ones.
Remedy AR System File Extensions
Extension Description
.arh History files (Login session and Saved Searches
.arm Mapping
.arq Macro files created from Remedy User
.arr Report Layout
.arv View caching
.arx AR Export
.dll Data Library Files
.js JavaScript Files
.jsp Java Server Pages
.lst Notifications queue
.rep AR Report
.rpt BO Crystal Report
.srh Query
Complied long back, I have used this reference several times, hope you also find them useful. 
Njoy
Venkat
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