Brocade FICON Administrator’s Guide (Supporting Fabric OS v7.3.0) - Manual (Page 80)

• During the firmware download process, a failover to the backup processor occurs. Any
outstanding CUP commands are lost which results in a timeout. To avoid this, CUP should be
varied offline before starting a firmware download. The CUP may be varied back online after a
successful firmware download.
• All firmware downloads cause an I/O disruption when the new code is activated on the Brocade
7800 switch and FX8-24 blade. However, the Brocade 7840 switch supports the FCIP Hot Code
Load (HCL) feature which allows firmware downloads without I/O disruption.
NOTE
If upgrading multiple switches or blades, upgrade one at a time. This is not a requirement for the DCX
or DCX-4S platforms.
Non-disruptive firmware upload and download
All systems maintain a primary and a secondary partition of nonvolatile storage areas. The following
overview of the firmware download process illustrates the use of the two partitions:
1. The firmware is downloaded to the secondary partition.
2. The current secondary and primary partitions are swapped.
3. The CP then reboots. In dual-CP systems (Brocade DCX Backbones), the backup CP is rebooted
with the new firmware and the HA failover is automatically invoked.
4. Once rebooted, the primary code image is copied to the secondary.
Considerations for fixed-port switches
Unlike director-class products, such as Brocade DCX Backbones, fixed-port switches have only one
control processor (CP) so they behave differently during Fabric OS hot code upgrades. This can
impact FICON operations if best practices are not followed.
During the code upload process, there is a period of time when the CP is busy rebooting the operating
system and re-initializing Fabric OS, and CP is not available to respond to CPU-targeted queries or
frames. For dual-CP products, this "busy" time is a couple of seconds (the time it takes for mastership
to change), and is non-disruptive. For single-CP fixed-port switches, however, the "busy" period can
last a minute or two. During this time, data traffic continues to flow uninterrupted, unless a response
from the CP is required. If a response from the CP is required, for path and device validation for
instance, Interface Control Checks (IFCCs) are possible. Any IFCCs should be recovered
automatically by the System z host, with no required user action.
This does not mean that switches are not appropriate for FICON. Fully certified FICON switch
deployments will continue to be sold and supported. It is important to follow the best practices of
performing the firmware upgrade during scheduled maintenance windows when traffic is minimized,
IFCCs can be tolerated, and the CUP is turned off.
Configuration restoration in a FICON environment
The following table describes the behavior of the configUpload and configDownload commands and
IPL file function when the ASM bit is set on or off. In general, if the switch is operating in a FICON
CUP environment and the ASM (Active=Saved) bit is set on, then the switch ignores the IPL file
downloaded when you restore a configuration.
Non-disruptive firmware upload and download
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