ASM Targets Show Down Status in 12c OEM after Grid Infrastructure Upgrade From 12.1.0.2 to 12.2.0.1 With Error: ORA-28040

Solution

Set the SQLNET.ALLOWED_LOGON_VERSION parameters explicitly to 8 in the sqlnet.ora file:

SQLNET.ALLOWED_LOGON_VERSION_SERVER=8
SQLNET.ALLOWED_LOGON_VERSION_CLIENT=8

Reloading the listener will fix the issue.