text: (cid:2) Over provisioned ratio 
  
  The ratio of provisioned capacity to usable capacity in the pool or system. 
  
  (cid:2) Provisioning limit - maximum provisioned capacity - over provisioning limit 
  
  In some storage systems, restrictions in the storage hardware or configured by the user 
  that define a limit the maximum provisioned capacity allowed in a pool or system. 
  
  **Capacity licensing**
  Capacity licensing is a licensing model that licenses features with a price-per-terabyte model. 
  Licensed features are FlashCopy, Metro Mirror, Global Mirror, and virtualization. See also 
  “FlashCopy” on page 776, “Metro Mirror” on page 780, and “Virtualization” on page 787. 
  
  **Chain**
  A set of enclosures that are attached to provide redundant access to the drives inside the 
  enclosures. Each control enclosure can have one or more chains. 
  
  **Challenge Handshake Authentication Protocol**
  Challenge Handshake Authentication Protocol (CHAP) is an authentication protocol that 
  protects against eavesdropping by encrypting the user name and password. 
  
  **Channel extender**
  A channel extender is a device that is used for long-distance communication that connects 
  other storage area network (SAN) fabric components. Generally, channel extenders can 
  involve protocol conversion to asynchronous transfer mode (ATM), Internet Protocol (IP), or 
  another long-distance communication protocol. 