Installation and Upgrade > Installation and Configuration Guide - Update Existing Installation > Updating an Existing Installation > Preparing Your System for the Update > Capture Non-modeled Indexes and Custom Sequences
  
Capture Non-modeled Indexes and Custom Sequences
If you have manually added non-modeled indexes or custom sequences to your database, they will be dropped during the update. You will be instructed to manually recreate them later to complete your update.
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If this situation applies to your setup, you MUST complete the following. Failure to do so will cause your manually added non-modeled indexes and custom sequences to be dropped.
1. Fully document any non-modeled indexes and custom sequences that you created for performance or other reasons. Since the database schema from PTC may have changed between releases, you must test that the objects you are going to create are defined correctly and are still needed in the context of the new release.
2. Create or locate SQL schema definition scripts to recreate the indexes and sequences. These will need to be executed later.
3. Identify the generated last number for each custom sequence, and adjust sequence definition scripts by resetting the start value.
4. Custom sequences must be noted and will be recreated as part of executing the final update steps. You can ignore the obsolete sequences.
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The list of indexes and custom sequences that have been dropped will be available in the Upgrade Database Schema Report that is created when you run the Update Tool. The custom sequences are listed in the Obsolete Sequences section of the Upgrade Database Schema Report along with obsolete PTC sequences.