Permissioned ledgers are covered mainly under permissioned blockchain, the most common form of the idea. This page explains the broader term, which also includes shared ledgers that do not chain records into blocks.
A permissioned ledger is a form of distributed ledger technology in which an operator or a group of members decides who may join, who may see which records and who may confirm new entries. Participants are identified, often legally bound by membership agreements, and usually subject to KYC checks. Because validators are known, these systems can use faster agreement methods than the mining or staking of open networks.
Banks, market infrastructure providers and supply chain groups use permissioned ledgers to share data and settle transactions among themselves without a single central database. Frameworks such as Hyperledger Fabric and R3's Corda are common foundations, and when several organisations run one jointly it is often called a consortium blockchain. Critics argue that the more tightly a ledger is controlled, the less it differs from a conventional shared database; supporters reply that it still offers a common, tamper-evident record. The opposite model, open to anyone, is a public blockchain.