Oracle recommends that you complete these good practices guidelines for updating Oracle Database. These practices are recommended for both manual and DBUA upgrades.

• Back Up the Database
  Perform a full backup of the production database.
• Scenario Non-CDB Running the postupgrade_fixups.sql Script
  Review this procedure to understand how to use the postupgrade_fixups.sql scripts for Non-CDB databases.
• Gathering Dictionary Statistics After Upgrading
  To help to assure good performance, use this procedure to gather dictionary statistics after completing your upgrade.
• Regathering Fixed Objects Statistics with DBMS_STATS
  After an upgrade, or after other database configuration changes, Oracle strongly recommends that you regather fixed object statistics after you have run representative workloads on Oracle Database.
• Reset Passwords to Enforce Case-Sensitivity
  For upgraded databases, improve security by using case-sensitive passwords for default user accounts and user accounts.
• Add New Features as Appropriate
  Review new features as part of your database upgrade plan.
• Develop New Administrative Procedures as Needed
  Plan a review of your scripts and procedures, and change as needed.
• Set Threshold Values for Tablespace Alerts
  After an upgrade, thresholds for the upgraded Oracle Database Tablespace Alerts are set to null, disabling the alerts.
• Migrating From Rollback Segments To Automatic Undo Mode
  If your database release is earlier than Oracle Database 11g, then you must migrate the database that is being upgraded from using rollback segments (manual undo management) to automatic undo management.
• Configure Oracle Data Guard Broker
  InitialConnectIdentifier is replaced by DGConnectIdentifier, which affects upgrades from Oracle Database 10g.
• Migrating Tables from the LONG Data Type to the LOB Data Type
  You can use the ALTER TABLE statement to change the data type of a LONG column to CLOB and that of a LONG RAW column to BLOB.
• Identify Oracle Text Indexes for Rebuilds
  You can run a script that helps you to identify Oracle Text index indexes with token tables that can benefit by being rebuilt after upgrading to the new Oracle Database release..
• About Testing the Upgraded Production Oracle Database
  Repeat tests on your production database that you carried out on your test database to ensure applications operate as expected.