> I suspect there is a problem while setting the archive_command that resulting towards accumulating WAL .ready file in pg_xlog/archive_status directory itself.
I think archive_command has no effect on the non-primary server, and the problem described above is happening on standby. It's hard to suspect the restore_command as well, because the WAL segments are copied to the pg_xlog as a result of the restore_command, and therefore, it's working.
I agree with Alexey. There's nothing wrong with our archive_command. Not sure what's wrong though.