If you look at Oracle pattern (e.g. OracleRDBMS), you see that the Oracle database can be discovered by browsing through Oracle configuration files or looking at the oracle processes running in the host. This will not require Database credential. The database credential is needed if you want to enable sql queries for extended database discovery.
You have the option to disable/enable the sql queries for extended database discovery in the pattern. If you enabled it, but you don't have any database credential defined, then you will see the failures (as shown in your above screen shot).
It seems the sql queries for extended data is enabled by default. Our Oracle DBA will setup an account in the Oracle databases with READ permission for ADDM to run sql queries for extended database, but do not know what level (SIDs, schema, table etc..) in database requires the credential for sql queries?