Empty variables can be troublesome

Upgrading a 10.2.0.4 ERP test database to 11.2.0.2 today, and shortly after starting the upgrade via DBUA, got the following error:

ORA-16024: parameter LOG_ARCHIVE_DEST_1 cannot be parsed

I had chosen to disable archiving as one of the options for DBUA, but was really surprised to see this error. After a little bit of research I found Metalink Doc 96278.1.

Turns out this error was happening because we had log_archive_dest along with log_archive_dest_1 set -- the kicker was it was set to be blank. Here's the relevant info from the pfile:

*.log_archive_dest=''
*.log_archive_dest_1='LOCATION=/u01/app/oracle/admin//arch'

So the trick was to completely remove the entire *.log_archive_dest='' line from the pfile and DBUA was able to proceed with the upgrade without the ORA-16024 error.