Obsolete

The creator of an event handler can select this field when the handler is no longer needed.

When a handler is marked as obsolete, it is considered permanently inactive, and the system simply ignores it when it is encountered.

Caution: 
In general, if you no longer need an event handler, we recommend that you not delete the handler. An event handler that might be in use by others should never be deleted, because its deletion can cause problems in the system. Instead, use this option to make it obsolete.

It is important to avoid deleting handler metadata that has been exported and made available to other metadata authors because those authors may have already associated their own event handler metadata with yours, or they might do so in the future (before they import your next export). If their next import of your exported metadata removes a handler that is referenced by their handler's Keep With field, a broken link will occur. This, in turn, forces the AppMetadataSync utility to relegate their handler to "free floating" status, meaning its sequence is less controllable, especially if you (or another metadata author whose handlers are referenced by your handlers' Keep With field) later resequence your handlers.