DBUA failed in bringing up the database. Either the database is not running from Oracle Home or the correct pfile was not found

Symptoms:

When using dbua to upgrade a database, you might get a pop-up asking for the location of the init.ora, with a message like this:
"Either the database is not running from Oracle Home or the correct pfile was not found" 

Cause:
An earlier upgrade attempt failed, and a dbua file got left "in limbo"

Solution:
cd /u01/app/oracle/cfgtoollogs/dbua/logs

ls
PreUpgradeResults.html  sqls.log  trace.log  Welcome_mydb.txt

rm Welcome_mydb.txt

From MOS Note: [ID 1303325.1]