The hold down interval starts whenever the IGP initially is enabled with LDP-IGP synchronization. It is also started whenever LDP updates the IGP with an update indicating the interface status is not-in-sync. When the hold down time expires, the IGP resumes advertising the normal metric for the link.
You can configure the hold down time. When you initially configure the hold down time, the router starts the hold-down-timer on every not-in-sync interface at the time.
When you delete the hold down configuration, the router stops the hold-down timer on every interface that is running the hold-down timer running as if there is no hold down time configured. As a result, these interfaces have an infinite hold down time. For the not-in-sync interfaces with an expired hold-down time, IGP continues to advertise the normal metric.