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ESCON Multiple-Host Environment

With ESCON, a single ESCON attachment can be shared between multiple LPARS or system images. However, the printer cannot be shared between multiple PSF hosts at the same time. Procedures must be put in place to take the printer offline to the existing PSF host before it can be brought online to another PSF host. If this is not done, unpredictable print results can occur.

The printer ESCON configuration option for Multi-Host Environment ensures that an operator cannot inadvertently vary the printer online to multiple PSF hosts simultaneously. This allows the sharing of ESCON attachments without concern that operator error may cause print problems. Use of the Multi-Host Environment option requires support for printer ASSIGN and UNASSIGN in both the operating system and PSF.

Operating system support is provided with OS/390 V1 R3.0 (which may be VM guests) and higher. PSF support is provided in PSF 3.1.0 for OS/390 and higher and also with APAR OW29992 to PSF/MVS 2.2.

The Multi-Host Environment option should not be enabled unless all hosts connected to the printer support printer ASSIGN and UNASSIGN. Otherwise, PSF cannot access the printer.

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 varied on to the second host successfully until the operator drains and varies it off to the first host.

For more information on PSF/MVS ASSIGN and UNASSIGN support, see the PSF for OS/390 Customization Guide or the documentation for APAR OW29992 to PSF/MVS 2.2.