ESCON and FICON channel

An IBM® ESCON® or FICON® channel-attached printer can be shared among multiple PSFs on the same or different hosts, but it can be in use by only one PSF at a time. The operator manually controls this sharing by stopping PSF and varying the printer offline on one host and then varying the printer online and starting PSF on another host.

IBM printers with a FICON channel adapter, or an ESCON PCI channel adapter with microcode level 9.6 or later, have a multi-host feature that supports multiple concurrent paths to the same printer. When the multi-host feature is enabled, the printer allows only one PSF to use the printer at a time. Multi-host support is also available if an ESCON channel-attached printer is attached to a FICON Bridge channel. For more information about the FICON Bridge feature, see Planning for 9032 Model 5 Director, SA22–7295.

Note:

You should enable the multi-host feature only if systems connected to the printer have z/OS® installed (systems can be standalone or guests on VM/ESA). If the multi-host feature is enabled but one of the hosts does not have the correct software installed, PSF encounters printer errors and is not able to use the printer. For more information about the multi-host feature, see the Introduction and Planning Guide for your printer.

Exclusive access to a printer can also be obtained by enabling the multi-host feature and configuring the printer to come online at IPL. If multiple systems, which share a printer with the multi-host feature enabled and defined to come online at IPL, are IPLed concurrently, the first system to successfully issue the printer ASSIGN gets access to the printer. When defining the printer by using a hardware configuration definition (HCD), the OFFLINE parameter can be optionally specified to configure the printer to come offline or online during an IPL. The default is to have the printer come online at IPL.

When the printer is configured in multi-host mode, it is important to follow proper operational procedures, such as draining PSF and varying the printer offline before re-IMLing the printer. Otherwise, the printer ASSIGN could be lost, the printer could be boxed, and PSF might issue an ABEND024 RC617. For more information about reconfiguration and recovery procedures for a printer ASSIGN, see the z/OS MVS System Commands.