Multiple Host Environment

With ESCON or FICON, a single adapter can be shared between multiple LPARS or system images. However, the printer cannot be shared between multiple PSF hosts at the same time. Operational procedures must be put in place to take the printer offline to the existing PSF host before bringing it online to another PSF. Otherwise, unpredictable print results can occur.

The Multi-Host Environment configuration setting for the ESCON or FICON adapters insures that an operator cannot inadvertently vary the printer online to multiple PSF hosts simultaneously. This allows sharing of ESCON adapters without concern that operator error could cause print problems. The Multi-Host Environment setting for the adapter requires support for printer ASSIGN and UNASSIGN in both the host operating system and PSF. Do not enable the Multi-Host Environment setting unless all hosts connected to the printer support printer ASSIGN and UNASSIGN. Otherwise, PSF cannot access the printer.

Support for the ASSIGN and UNASSIGN functions is built into the host and printer for communication with TCP/IP Ethernet.

To allow access by a different PSF host, the operator must drain the printer and vary it off to one host before varying it on to the second host. A second host trying to vary on the printer is denied access with a notice that the printer is assigned elsewhere. The printer cannot be successfully varied on to the second host until the operator drains and varies it off to the first host. For more information on ASSIGN and UNASSIGN support, see PSF for z/OS customization information.