International Business Machines Corporation

Tim J Vincent

Matthew Albert Huras

Xun Xue

Hebert Walter Pereyra

Jon A Lind

Peter K L Shum

A gateway provides communication of tightly coupled XA transactions to a server hosting a DBMS and makes efficient use of domain socket pairs to implement demultiplexing in the gateway. The gateway includes a TCP/IP listener process which accepts connection requests from a transaction manager. Logical agents represent the application connection and are managed by a logical agent scheduler and are passed within the gateway using domain socket pairs. Gateway agents are dedicated to identified tightly coupled XA transactions to provide tightly coupled XA transaction support for DBMS systems which do not provide such support directly. The domain socket pairs in the gateway are assigned to logical agent schedulers and are available in a domain socket pool. A wait queue is provided to buffer logical agents when connection to the server is not available or where there are no domain socket pairs available in the domain socket pool. The wait queue is itself implemented as a domain socket pair.

Efficient use of domain socket pairs in communication for tightly coupled transactions

A service provider for use in a client-server system which is capable of detecting the abnormal termination of a client process is disclosed. The service provider does not require a dedicated process for polling client processes in order to verify their status. Rather, a semaphore, which is used in conjunction with a shared memory segment for communication between a client process and the service provider, is initialized in such a manner that the operating system will automatically increment the semaphore in the event the client process is terminated. Thus, the semaphore will be incremented either when the client process deliberately increments the semaphore in order to notify the service provider that the client process has written data to a shared memory segment, or the semaphore will be incremented by the operating system in the event the client process terminates. A test flag is established in shared memory in order to differentiate whether the semaphore was incremented by the client process, or by the operating system. The client process will set the flag only when the client process increments the semaphore. Therefore, whenever the semaphore is incremented, the service provider will test the condition of the flag, and terminate resources allocated to the client process if the flag is not set.

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Toronto, Canada

Tim J Vincent