Product Code Database
FICON ( Fibre Connection) is the IBM proprietary name for the ANSI FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre Channel (FC) protocol. It is a FC layer 4 protocol used to map both IBM's antecedent (either ESCON or parallel Bus and Tag) channel-to-control-unit cabling infrastructure and protocol onto standard FC services and infrastructure. The topology is switched fabric utilizing FC switches or directors. Valid rates include 1, 2, 4, 8, 16, and 32 Gigabit per second data rates at distances up to 100 km.
FICON was introduced in 1998 as part of System/390 G5 IBM mainframe. In July 2013, FICON replaced ESCON in new zEnterprise BC12/EC12, and later models, because of FICON's technical superiority (especially its higher performance) and lower cost.
FICON channels use five classes of IUs to conduct information transfers between a channel and a control unit. They are: Data, Command, Status, Control, and lastly Link Control. Only a channel port may send Command or Command and Data IUs, while only a control unit port may send Status IUs.
As with prior IBM mainframe channel protocols, there is a concept of a channel to control unit "connection". In its most primitive form, a connection is associated with a single channel program. In practice, a single channel program may result in the establishment of several sequential connections. This normally occurs during periods where data transfers become dormant while waiting for some type of independent device activity to complete (such as the physical positioning of tape or a disk access arm). In such cases, the connection may be closed by action of the device's control unit with the signaling of appropriate status. When the control unit is ready to resume such an interrupted connection, it signals the channel to reconnect and resume the interrupted channel program. By closing temporarily dormant connections, channel and control unit facilities may be better utilized to serve other active channel programs and certain protocol timeouts that might otherwise occur may be avoided.
FICON uses two Fibre Channel exchanges for a channel control unit connection one for each direction. So while a Fibre Channel exchange is capable of carrying a command and response on a single exchange, and all other FC-4 protocols work that way, the response to a FICON IU is always on a different exchange from the IU to which it is a response. The two exchanges that implement a connection are called an exchange pair (Note that the concept of the two exchanges being related exists only at the FC-4 layer). While other FC-4s have a single "data structure type" code that characterizes their IUs in Fibre Channel frame headers, FICON has two. One is for IUs from channel to control unit; the other for control unit to channel.
Except for some initialization dialogue that requires stronger synchronization, FICON uses Fibre Channel class of service 3 (Datagram). Thus, at the Fibre Channel physical (FC-2 and below) level, the communication is connectionless, frames and sequences may arrive out of order, and there is no acknowledgement of arrival. But all of that exists at the FC-4 level.
FICON is technically quite similar to more popular storage protocols, such as FCP. Both FICON and FCP share levels 1–3 of Fibre Channel specifications. Some administrators argue that FICON offers somewhat easier troubleshooting in mainframe environments, but the inherent technical advantages and disadvantages between FICON and FCP are much alike. Some mainframe-specific setups, such as GDPS, require FICON (or its predecessor ESCON). Mainframe-attached storage, such as IBM's System Storage DS8000, often supports both protocols. The storage is divided into fixed block storage volumes (accessed with FCP) and mainframe-specific CKD/ECKD storage volumes (accessed with FICON and/or ESCON).
Tape storage facilities include:
Hardware Security Module (HSM) products that support FICON include:
Switches/directors that support FICON include:
Other manufacturers producing FICON-compatible equipment include Optica Technologies, and InfoPrint Solutions Company, which offers high-volume printers that can attach via FICON.
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