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OMI - Shared Resources

Draft MDC Standard

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B.5 Shared resources

Transactions are isolated (see 4.3.3), but the lock transaction (5.4.18) 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.

Similarly, the open device transaction implies a device manager that associates devices with the clients that own them and resolves requests for devices. OMI simply transports the requests.

The device transactions support shared devices – those that more than 1 client may "own" simultaneously – by including the client identifier in each transaction.

Implementers of client nodes should consider what to send to the lock manager and device manager when clients terminate normally or abnormally, and when disconnecting a session for different reasons. OMI's requests to unlock client, unlock all, close client's devices, and close all devices are provided to simplify the agent, which would otherwise have to remember what resources its clients hold on the server's node.

Implementers of servers should address the matter of outstanding locked nrefs and devices owned 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.

Some specifications are "approved for inclusion in a future standard". Note that the MUMPS Development Committee cannot guarantee that such future standards will indeed be published.

This page most recently updated on 13-Sep-2014, 14:30:34 .

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