Leave the application and its environment unchanged.

Do not relink, precompile, or compile the application, and do not change the application code. The application continues to work against the new Oracle Database 12c. This option requires that the Oracle home environment of the application is not upgraded. You can leave the application unchanged, and it continues to work with the Oracle Database 12c server. The major advantage to this option is that it is simple and easy. In addition, this option requires the least amount of administration, because you are not required to upgrade any of your client computers. If you have a large number of client computers, then avoiding the administrative costs of upgrading all of them can become very important.

The major disadvantage to this option is that your application cannot use the features that are available in the new release of Oracle Database. In addition, your application cannot leverage all the possible performance benefits of Oracle Database 12c.

Application code must be changed if any APIs are deprecated or changed.

Precompile or compile, and then relink the application using the new release of Oracle Database. When upgrading to the new release of Oracle Database software, you must precompile or compile the application with the new software after making necessary code changes to account for APIs that are deprecated or changed.

This option requires that you install the new Oracle Database client software on each client computer. You are required to precompile or compile, and relink your application only one time, regardless of the number of clients you have.

By recompiling, you perform a syntax check of your application code. Some problems in the application code that were not detected by previous releases of the Oracle software can emerge when you precompile or compile with the new Oracle Database software. Precompiling and compiling with the new software helps you detect and correct problems in the application code that previously were unnoticed.

Also, recompiling affords maximum stability for your application, because you are sure that it works with the new Oracle Database release. Further, your environment is ready for new development using the latest tools and features available. In addition, you might benefit from performance improvements that are available with the new Oracle software only after you recompile and relink.

Make code changes to your applications to take advantage of new Oracle Database features.

Change the application code to use new features in Oracle Database 12c. Then, precompile or compile and then relink the code. This option is the most difficult, but it can provide the most potential benefits. You gain all of the advantages described in Option 2: Precompile or Compile the Application Using the New Software. . In addition, you also benefit from changes to your application that may leverage performance and scalability benefits available with the new release of Oracle Database. Further, you can add new features to your application that are available only with the new release. Consult the Oracle documentation for your development environment so that you understand how to implement the features you want to use.

When you have decided on the new features to use, change the code of your application to use these features.

Follow the appropriate instructions in the following sections based on your development environment.

• Changing Precompiler Applications
  Complete these steps to change precompiler applications to use new Oracle Database release features.
• Changing OCI Applications
  To use new features in your new Oracle Database release, you must recompile your applications with the OCI calls for the new Oracle Database release.