Hi Jithin,
I think information below is the fatal ones:
FAL[server, ARC0]: Error 12518 creating remote archivelog file 'dev_mmsr18'
FAL[server, ARC0]: FAL archive failed, see trace file.
ARCH: FAL archive failed. Archiver continuing
You may need to check whether standby have physical access to the remote archived log directory.
Best regards,
James