If you use the Oracle Applications Object Library Audit Trail feature, you must disable it before the upgrade. From the System Administrator responsibility under the 11i APPL_TOP, navigate to Security > Audit Trail > Groups. In the Audit Groups window, set the Group State field to Disable - Prepare for Archive for each audit group defined. Run the Audit Trail Update Tables report from the Submit Requests window (Requests > Run). If you plan to re-enable auditing after the upgrade, then archive and purge the shadow tables now. Data changes made after implementing this step are not audited. Note: See Audit Trail in Oracle E-Business Suite System Upgrading to Release 12.1.1 3-3 Administrator's Guide - Security.
Question isDisable it in the 11i instance before the upgrade, then you can enable it again after R12 upgrade. Whatever is mentioned above, it needs to be done before the upgrade.
a) Do I have to run this in the test upgrade instance of 11i?
or do I have to run in the 12i instance with newly layed out file system ?