Thank you for the post.
The file is opened by the fmswpc.exe FileMaker Server 11 Advanced process. If FileMaker Server 11 Advanced is first stopped, then the log can be moved.
Additionally, the FileMaker Server 11 Advanced Admin Console has a setting to limit the log size:
Configuration > Web Publishing > General Settings > "Log Size:"
For more information, review "Logging and statistics settings" on page 69 of the FileMaker Server 11 Advanced Help Guide.
Last year I set the size you indicated to 40 MB. The wpc_access_log.txt file is now over 800 MB. What do I need to do to limit the size of this file? I'm running FM server advanced 12. Windows says, as you mentioned, that the file was opened by fmwxpc.exe.
AFIK, the log size is just for the FM Server log. Other logs (wpe, etc) will fill every Disk if something goes mad. Logging can be disabeled, IMHO the only solution (at least with FMS11)
We have had this back in 2011 - we had to disable the log's. Runs fine now, although debugging is no longer possible (iwp)