Archive logs FORMAT

You use LOG_ARCHIVE_FORMAT parameter to specify how will the archive log files look like. You have the following possible variables:

%s log sequence number
%S log sequence number, zero filled
%t thread number
%T thread number, zero filled
%a activation ID
%d database ID
%r resetlogs ID that ensures unique names are constructed for the archived log files across multiple incarnations of the database

There is not a single word in the document that some of the variables are actually REQUIRED
So after setting it to something like

ALTER SYSTEM SET log_archive_format='%d_%s_%r.arc' SCOPE=SPFILE;

After restarting the instance you will get an error like this:

ORA-19905: log_archive_format must contain %s, %t and %r

Why not to do the check when the parameter is actually set? Instead oracle chooses to check it on startup and you end up with an unstartable instance. You also cannot restore the spfile from autobackup, because rman needs instance running at least in NOMOUNT mode. The only option is to boot with a pfile (no matter where you'll get it) . But this is the only solution oracle offers you

It also seems that you cannot affect the format of archive logs saved to the DESTINATION 10, which is set to USE_DB_RECOVERY_FILE_DEST value. It must be that oracle manages filenames on his own inside the recovery area.