Most ITIM/ISIM gurus will understand what goes on during Service reconciliation. Let's be honest, most gurus have had to write countless adapters and perform countless bouts of debugging problems when they arise.
What happens, though, if you have one ISIM environment that can reconcile a service successfully but a second ISIM environment which cannot reconcile the exact same service. And let us, for a moment, assume that both ISIM environments are configured identically.
Of course, if something works in one environment and doesn't work in another, there must be a difference somewhere. But the ISIM version is the same, the service profile is the same, the service definition is the same, it's talking to the same TDI instance which performs the grunt work of retrieving all the data from the target service. On the face of it - there is no reason for one environment to behave any differently than the other.
Yet it can happen! In fact, I recently saw an ISIM environment get itself into a hung state trying to reconcile a service yet all the reconcilable objects had made their way into ISIM.
When ISIM reconciles a service, the result is that supporting data objects are stored in the LDAP under the service container (erglobalid=123,ou=services,erglobalid=00000000000000000000,ou=org,dc=com) and ultimately accounts are stored under the ou=accounts and ou=orphans containers. I say ultimately for a reason. The accounts are actually temporarily stored under the service container too before being moved to a more appropriate container.
And therein lay the difference in my two environments. The working environment had no accounts stored under the service container prior to executing the reconciliation. Somehow, the non-working environment did have some accounts left hanging about under the service container.
A ruthless LDAPDELETE on all objects sub-ordinate to the service was all that was required for the reconciliation to complete successfully.
Next time you have a misbehaving reconciliation process, why not check to see how previous reconciliations have been left by having a look under your service container. You might be surprised at what you will find.