What

In the Configurable Person Synchronisation cron job (Found in Administrator > Jobs > Job scheduling) under Job configuration > Data provider configurations there is a setting for ‘Legacy synchronisation sources.’

Why

If synchronising with an old synchronisation you will want to include the source of the old synchronisation in the 'legacy synchronisation sources' field so that the synchronisation will take over the IDs from the old/legacy synchronisation.

In this field, you would simply add the source; e.g. as depicted in the 'source' field on the piece of content.

Note This field only needs to be used when switching from an old synchronisation and is not necessary when switching data providers (e.g. when the client goes from using a database to using XML).

More information

KB-87 Transitioning to the Configurable Synchronisation
KB-93 General Configurable Synchronisation errors
Migrating from old to unified synchronisation
Note: Some of this information is for internal use only and might not be accessible.