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Mainframe Solutions

FICON Dynamic Routing: Here at Last

by Dr.Steve.Guendert on ‎09-08-2016 11:20 AM (4,255 Views)

FICON Dynamic Routing is now suppored by IBM z Systems and Brocade. IBM and Brocade just published a new joint white paper titled FICON Dynamic Routing (FIDR): Technology and Performance Implications.  I had the privelege of working with P.J. Catalano from the IBM z Systems team in Poughkeepsie on writing this paper.  


As many of you know, we have been working on FIDR for a few years now.  The Brocade term is Exchange Based Routing (EBR), and is something we have supported for open systems/FCP traffic for many years.  It is great to have it supported for FICON.  A special thanks goes out to the IBM z Systems teams and the Brocade engineering teams for all of the hard work they did to bring this to fruition.  


I will not go into the technical details of FIDR here because I believe it best if you download the paper and read it.  If you have questions after reading the paper, please let me know.


FIDR Basics


As part of the z13 announcement in January 2015, IBM announced a new FICON routing technique for FICON interswitch links (ISLs) called FICON Dynamic Routing (FIDR). FIDR enables ISL routes to be dynamically changed based on the Fibre Channel exchange ID, which is unique for each I/O operation. With FIDR, an ISL is assigned at I/O request time, so different I/Os from the same source port going to the same destination port may be assigned different ISLs.  


z13 servers using FIDR have advantages for performance and management in configurations with ISL and cascaded FICON directors:

• Support sharing of ISLs between FICON and FCP (Metro Mirror/PPRC or distributed)

• I/O traffic is better balanced between all available ISLs • Improve utilization of FICON directors and ISLs

• Easier to manage with a predictable and repeatable I/O performance


FICON dynamic routing can be enabled by definition of dynamic routing capable switches and control units in HCD. Also, z/OS has implemented a health check function for FICON dynamic routing.


The paper discusses requirements for FIDR, reviews the basics of cascaded FICON, explains how the predecessor technology (static routing) works, and compares it with the new FICON Dynamic Routing mechanism. The paper  concludes with a discussion of design considerations and the possible use cases where implementing FICON Dynamic Routing will be of the most benefit to z Systems end users. It is available for download on the IBM Tech Docs website.  I also have attached it to this blog post.


If you have any questions, please email me at If you use Twitter, you can follow me @DrSteveGuendert.  I'll be "tweeting" on FIDR and other z Systems topics. 


Thanks for reading.


Dr. Steve