Berkeley DB Family

hi

I am using Berkeley DB (libdb_cxx5.3) on linux

__db.originBDBfilename file are created intermittently.

so, I read the reference guide

I found internal files such as __db.001 or __db.rep.db.

but, I can not find about just  origin filename with '__db.' prefix.

what is "__db.originBDBfilename" file?

and why this file is created?

and Is it okay just delete this __db file?

thanks.