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OMI - Protocol Stack

1995 Version of ANSI (Equivalent to Current ISO Version) of Standard

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B.4 Protocol stack

The designers of OMI intend it to work well in implementations that include other network services, including proprietary protocols providing the same database functions. Because OMI relies on an externally supplied transport protocol, its success at sharing network hardware and software depends on the generality of the vendor's network software services.

OMI network managers face a more complex task than those purchasing a proprietary network from one vendor who takes responsibility for making everything work. As with any mixed-vendor system, the customer assumes that responsibility or pays a system integrator to do so. For a successful network the vendors must offer – and the customer must choose – a compatible stack of protocols at the transport level and at each lower level down to the hardware connection. (Gateways between unlike protocols are available.) Any method that provides an error-free, sequence-preserving path for messages containing all 8-bit characters is suitable.

Note – Therefore, a serial line interface could not use special characters for flow control or other purposes unless a protocol below OMI mediates to permit all 256 characters for OMI messages.

Transactions are isolated (see 4.3.3), but the lock operation (5.4.13) implies a lock manager that associates nrefs with the clients that have claimed them and denies other claims. The designers assume the lock manager to reside on the server's node. The OMI server relies on the lock manager to resolve lock requests; OMI simply transports them.

Implementers of client nodes should consider what to send to the lock manager when clients terminate normally or abnormally, and when disconnecting a session for different reasons.

Implementers of servers should address the matter of outstanding locked nrefs when a session terminates due to circuit failure. It may be prudent to give the network manager the choice of keeping them or dismissing the claims.

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Copyright © Standard Documents; 1977-2018 MUMPS Development Committee;
Copyright © Examples: 1995-2018 Ed de Moel;
Copyright © Annotations: 2003-2008 Jacquard Systems Research
Copyright © Annotations: 2008-2018 Ed de Moel.

This page most recently updated on 13-Sep-2014, 14:30:23 .

For comments, contact Ed de Moel (demoel@jacquardsystems.com)