International Business Machines Corporation

Jon A Lind

Xun Xue

Hebert Walter Pereyra

David C Kalmuk

Steven Robert Pearson

Vincent Kulandaisamy

Dale Murray McInnis

Yuke Zhuge

Steve Raspudic

Tim J Vincent

Peter K L Shum

An operating system directed to using special properties of a common inter-process communications mechanism (IPC), namely UNIX domain socket-pairs or stream-pipes alternatively as a storage medium for file-descriptors of UNIX processes. When a file-descriptor is written into a socket-pair, and closed in the UNIX process, the file remains open, but occupies no space in the process' file-table. The file-descriptor may later be read out of the socket-pair to reestablish it in the file-table, and access it. This property is implemented in an IPC mechanism of UNIX operating system whereby a process such as a dispatcher may manage more connections and processes than its file-table size allow. This provides scalability improvements of the UNIX operating system.

Method and system for optimizing file table usage

A method, system, and computer program product for reducing likelihood of data loss during performance of failovers in a high-availability system comprising a primary system and a standby system are provided. The method, system, and computer program product provide for defining a halt duration, periodically determining a halt end time, halting data modifications at the primary system responsive to failure of data replication to the standby system, resuming data modifications at the primary system responsive to a last determined halt end time being reached or data replication to the standby system resuming, and responsive to the primary system failing prior to a previously determined halt end time, determining that a failover to the standby system will not result in data loss on the standby system with respect to the primary system.

Reducing likelihood of data loss during failovers in high-availability systems

A communications multiplexor includes dispatcher processes for monitoring client connections. The dispatcher processes detect activity on those connections, and then pass active physical (client) connections to agent processes for servicing. Transfer is done through specific connection queues that are associated with a set of agents. A multi-queuing structure permits pooling of agents on a set of shared resources thereby reducing time required to switch between different client connections. After an agent has serviced a given connection, the agent returns that connection to the agent's dispatcher (there is a static assignment between connections and dispatchers), and then reads the next unit of work from the agent's associated connection queue. This structure may be scalable while allowing optimal performance when passing physical connections between processes.

Communication multiplexor using listener process to detect newly active client connections and passes to dispatcher processes for handling the connections

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

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Beaverton, OR, United States of America

Jon A Lind