Here is a plain guide to the records that decide most property questions in AP.
Adangal and Pahani
These are the village level land records maintained by the revenue authorities. The adangal, also referred to as the pahani, records details for each survey number: the pattadar, the extent, the land classification, the crops grown and the nature of possession. It is a snapshot of the current state of the land in the revenue records, and one of the first documents to examine when verifying a property.
Patta and the Pattadar Passbook
The patta is the revenue department's record of who holds the land, and the passbook is the physical document issued to that holder. Here is the point that trips up many buyers: a patta is not the same as title. It is strong evidence of possession and of the revenue department's recognition of a holder, but ownership ultimately flows from the registered sale deeds. Patta and title should agree, and when they do not, there is a problem to investigate before proceeding.
FMB, the Field Measurement Book
The FMB is the survey record showing the exact shape, boundaries and measurements of a survey number. It is what you use to confirm that the land on the ground matches the land on paper. Boundary disputes, and extent shortfalls where you receive less land than the deed promised, are resolved by reference to the FMB.
Mutation
Mutation is the process of updating the revenue records to reflect a change of ownership after a sale, inheritance or gift. When you buy, mutation records the change from the seller's name to yours. A sale that is registered but never mutated leaves the revenue records showing the previous owner, a mismatch that causes serious complications later. Applying for mutation after purchase is not a formality to be skipped.
The registered deeds establish ownership, the patta and adangal show possession and revenue recognition, the FMB confirms the physical extent, and mutation keeps the record current. A safe property is one where all of these align. Where they contradict one another, that contradiction is precisely where disputes are born.
You do not need to become a revenue expert to buy land safely, but you do need someone who can read these records together and identify the inconsistencies, because most title problems are visible in the records long before they reach a court.