What is revival letter ( in respect of occ a/c)

As per law of limitation a Demand promissory note is valid for a period of 3 years only.

A  fresh set of documents must be obtained before the expiry of 3 years.

A revival letter is taken from the customer or gurantor to the effect that the Demand Promissory note taken by bank at the time of issuing loan shall be continuing security.