What Is SID History in an AD Migration?

Every Active Directory account has a security identifier (SID). Permissions on file shares, printers and applications point to that SID. A new account in the target domain gets a new SID, so it cannot reach resources that still sit in the source domain.

SID history copies the source SID onto the target account. Windows then treats both SIDs as the same user, so migrated users keep access to source resources until you move or re-permission them.

You need it when users move domains before their resources do, which is common in mergers and phased migrations. It needs several settings on the source and target PDC emulators. PowerSyncPro provides a script that checks them from the PowerSyncPro server and both PDC emulators.

SID history is a temporary measure. Remove it once resources are re-permissioned. PowerSyncPro DirSync syncs SID history between forests as part of user synchronisation.