IBM Z10 BC manual Distance, Ficon Express enhancements for Storage Area Networks

Extended distance FICON – improved performance at extended

distance

An enhancement to the industry standard FICON architec- ture (FC-SB-3) helps avoid degradation of performance at extended distances by implementing a new protocol for “persistent” Information Unit (IU) pacing. Control units that exploit the enhancement to the architecture can increase the pacing count (the number of IUs allowed to be in fl ight from channel to control unit). Extended distance FICON also allows the channel to “remember” the last pacing update for use on subsequent operations to help avoid degradation of performance at the start of each new operation.

Improved IU pacing can help to optimize the utilization of the link, for example help keep a 4 Gbps link fully utilized at 50 km, and allows channel extenders to work at any dis- tance, with performance results similar to that experienced when using emulation.

The requirements for channel extension equipment are simplifi ed with the increased number of commands in

flight. This may benefi t z/OS Global Mirror (Extended Remote Copy – XRC) applications as the channel exten- sion kit is no longer required to simulate specifi c channel commands. Simplifying the channel extension require- ments may help reduce the total cost of ownership of end- to-end solutions.

Extended distance FICON is transparent to operating sys- tems and applies to all the FICON Express2 and FICON Express4 features carrying native FICON traffi c (CHPID type FC). For exploitation, the control unit must support the new IU pacing protocol. The channel will default to cur- rent pacing values when operating with control units that cannot exploit extended distance FICON.

Exploitation of extended distance FICON is supported by IBM System Storage DS8000 series Licensed Machine Code (LMC) level 5.3.1xx.xx (bundle version 63.1.xx.xx), or later.

To support extended distance without performance degra- dation, the buffer credits in the FICON director must be set appropriately. The number of buffer credits required is dependent upon the link data rate (1 Gbps, 2 Gbps, or 4 Gbps), the maximum number of buffer credits supported by the FICON director or control unit, as well as application and workload characteristics. High bandwidth at extended distances is achievable only if enough buffer credits exist to support the link data rate.

FICON Express enhancements for Storage Area Networks

N_Port ID Virtualization

N_Port ID Virtualization is designed to allow for sharing of a single physical FCP channel among multiple operating system images. Virtualization function is currently available for ESCON and FICON channels, and is now available for FCP channels. This function offers improved FCP channel utilization due to fewer hardware requirements, and can reduce the complexity of physical FCP I/O connectivity.

Program Directed re-IPL

Program Directed re-IPL is designed to enable an operat- ing system to determine how and from where it had been loaded. Further, Program Directed re-IPL may then request that it be reloaded again from the same load device using the same load parameters. In this way, Program Directed re-IPL allows a program running natively in a partition to trigger a re-IPL. This re-IPL is supported for both SCSI and ECKD devices. z/VM 5.3 provides support for guest exploitation.

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