Check that required operating system environment variables point to the directories of the new Oracle Database release.

Confirm that the following Oracle user environment variables point to the directories of the new Oracle home:

• ORACLE_HOME

• PATH

It is possible that packages that you installed in the earlier release Oracle Database are not available in the new release, which can affect applications.

After the upgrade, if you use AutoUpgrade, review the AutoUpgrade report on invalid objects. If you use a replay upgrade, then check to ensure that any packages that you may have used in your own scripts, or that you call from your scripts, are available in the new release. Testing procedures dependent on packages should be part of your upgrade plan.

Code in database applications can reference objects in the connected database. For example, Oracle Call Interface (OCI) and precompiler applications can submit anonymous PL/SQL blocks. Triggers in Oracle Forms applications can reference a schema object. Such applications are dependent on the schema objects they reference. Dependency management techniques vary, depending on the development environment. Oracle Database does not automatically track application dependencies.

If you created statistics tables using the DBMS_STATS.CREATE_STAT_TABLE procedure, then upgrade these tables by running DBMS_STATS.UPGRADE_STAT_TABLE.

EXECUTE DBMS_STATS.UPGRADE_STAT_TABLE('green', 'stat_table'); 

Oracle Database Configuration Assistant (DBCA) does not configure ports for Oracle XML DB on Oracle Database 12c and later releases. Upgrades use digest authentication.

Oracle recommends that when you configure ports, you also configure the authentication for HTTP for accessing Oracle XML DB Repository to take advantage of improved security features.

Starting with Oracle Database 12c, Oracle enhanced database security by supporting digest authentication. Digest authentication is an industry-standard protocol that is commonly used with the HTTP protocol. It is supported by most HTTP clients. Digest authentication ensures that passwords are always transmitted in a secure manner, even when an encrypted (HTTPS) connection is not in use. Support for digest authentication enables organizations to deploy applications that use Oracle XML DB HTTP, without having to worry about passwords being compromised. Digest authentication support in Oracle XML DB also ensures that the Oracle XML DB HTTP server remains compatible with Microsoft Web Folders WebDAV clients.

After installing or upgrading for the new release, you must manually configure the FTP and HTTP ports for Oracle XML DB as follows:

1. Use DBMS_XDB_CONFIG.setHTTPPort(HTTP_port_number) to set the HTTP port for Oracle XML DB:

   SQL> exec DBMS_XDB_CONFIG.setHTTPPort(port_number);
   

2. Use DBMS_XDB_CONFIG.setFTPPort(FTP_port_number) to set the FTP port for Oracle XML DB:

   SQL> exec DBMS_XDB_CONFIG.setFTPPort(FTP_port_number);
   

   Note:

   You can query the port numbers to use for FTP and HTTP in the procedure by using DBMS_XDB_CONFIG.getFTPPort and DBMS_XDB_CONFIG.getHTTPPort respectively.

3. To see all the used port numbers, query DBMS_XDB_CONFIG.usedport.

After an Oracle Database upgrade, all user extensions to the Oracle Text supplied knowledge bases must be regenerated.

Regenerating the user extensions affect all databases installed in the given Oracle home.

After an upgrade, the Oracle Text-supplied knowledge bases that are part of the companion products for the new Oracle Database are not immediately available. Any Oracle Text features dependent on the supplied knowledge bases that were available before the upgrade do not function after the upgrade. To re-enable such features, you must install the Oracle Text supplied knowledge bases from the installation media for the new Oracle Database release.

Oracle Database 12c and later releases include fine-grained access control to the UTL_TCP, UTL_SMTP, UTL_MAIL, UTL_HTTP, or UTL_INADDR packages.

If you have applications that use these packages, then after upgrading Oracle Database you must configure network access control lists (ACLs) in the database before the affected packages can work as they did in earlier releases. Without the ACLs, your applications can fail with the error "ORA-24247: network access denied by access control list (ACL)."

Depending on your target database release, you can be required to disable Oracle Database Vault to complete an Oracle Database upgrade.

• Upgrading Oracle Database Without Disabling Oracle Database Vault
  If your target Oracle Database release is 12.2 or later, then you can upgrade without disabling Oracle Database Vault.
• Common Upgrade Scenarios with Oracle Database Vault
  The requirements to enable Oracle Database Vault after upgrades change, depending on your source Oracle Database release.

Connections to Oracle Database from clients earlier than release 10g fail with the error ORA-28040: No matching authentication protocol.

Starting with Oracle Database 18c, the default value for the SQLNET.ALLOWED_LOGON_VERSION parameter changed from 11 in Oracle Database 12c (12.2) to 12 in Oracle Database 18c and later releases. The use of this parameter is deprecated.

SQLNET.ALLOWED_LOGON_VERSION is now replaced with the SQLNET.ALLOWED_LOGON_VERSION_SERVER and SQLNET.ALLOWED_LOGON_VERSION_CLIENT parameters. If you have not explicitly set the SQLNET.ALLOWED_LOGON_VERSION_SERVER parameter in the upgraded database, then connections from clients earlier than release 10g fail with the error ORA-28040: No matching authentication protocol. For better security, check the password verifiers of your database users, and then configure the database to use the correct password verifier by setting the SQLNET.ALLOWED_LOGON_VERSION_SERVER and SQLNET.ALLOWED_LOGON_VERSION_CLIENT parameters.

If you have password-protected roles (secure roles) in your existing database, and if you upgrade to Oracle Database 18c and later releases with the default SQLNET.ALLOWED_LOGON_VERSION_SERVER setting of 12, because those secure roles only have release 10g verifiers, then the password for each secure role must be reset by the administrator so that the secure roles can remain usable after the upgrade.