BEA TUXEDO system applications are modular and extensible; the BEA TUXEDO system provides a natural way to structure the many different components of a distributed OLTP or general-purpose client/server application into well-defined units or programs.
When the BEA TUXEDO system is used with a commercial UNIX DBMS, the BEA TUXEDO system enhanced client/server architecture demands much less in the way of system resources than the same DBMS without the BEA TUXEDO system. This is because relatively few BEA TUXEDO system servers can service literally hundreds of clients. In fact, in benchmark tests with commercial UNIX DBMSs, the BEA TUXEDO system has increased performance, measured in transactions per second, by a factor of 40.
Figure 1 provides a high-level glimpse of the client/server architecture.
Figure 1 Client/Server Architecture
Web-based Graphical User Interface for Administration
The Administration Console is a new interface for the configuration and administration of BEA TUXEDO applications. It provides a helpful set of tools, principal among which are the "Tree" and the "Configuration Tool." The Tree is a graphical depiction of the hierarchical composition of the objects that make up a BEA TUXEDO application. The Configuration Tool is a set of "tabbed folders" on the screen that display data and prompt the administrator for the information needed to configure any class of administrative objects. In addition, the context-sensitive help feature allows the user to get detailed information about any GUI tool or field for which input is required.
Event Broker/Monitor
The BEA TUXEDO system has defined a set of almost three dozen system events that are detected and reported on. The list of system events tracked is published in EVENTS(5). When an event is detected the Event Broker/Monitor is informed by the system; it, in turn, passes the information along to any subscribing processes. An event can be as innocuous as a change in the system configuration or as potentially harmful as a failure in the system network. Subscribers sign up to receive information for as many of the monitored events as they are interested in. They can also choose to receive notification in several ways: it can be sent via unsolicited notification, it can be queued to stable storage via the Queue Management facility, or the event can be used to kick off a service. To illustrate, notice of a message queue blockage could be used to start a server that activates more servers in that group. An application also has the ability to define its own set of events, publish a list like that in EVENTS(5), and allow users to subscribe.
Management Information Base (MIB)
The BEA TUXEDO system can be conceptually divided into several major components or subsystems such as the core system, Workstation, /Q, and others. A component contains classes of objects; classes have attributes for which a range of values can be defined. When all of the classes and their objects are viewed as one larger object, that object is referred to as a MIB. There are several MIB entries in Section 5 of the BEA TUXEDO Reference Manual and probably the quickest way to grasp the idea of MIBs is to spend a few minutes with one of those entries.
The significance of the MIBs lies in the fact that they provide the framework for programmed administration of a BEA TUXEDO system. By changing the value of an attribute an administrator or operator can change the behavior of the system and can do it by executing programs written specifically to do so. A MIB entry in the BEA TUXEDO Reference Manual not only tells the allowed values for an attribute, it also tells the circumstances under which the value can be changed. For example, the description of the attribute TA_STATE in class T_SERVER of the TM_MIB tells how the administrator can use the attribute to change the state of a server (and provides a list of valid states.) It also says that the value can be changed by the administrator or the operator when the server is active; others can retrieve the state, but may not change it. The real power of this lies in the fact that a program can be written to make the change when some condition is detected.
Distributed Services
The BEA TUXEDO System provides for the connectivity of a network of loosely coupled computers running clients and servers within the framework of a single application. Application designers have great flexibility when choosing platforms on which to implement applications. BEA TUXEDO system networking libraries work with either the Transport Layer Interface (TLI) library or Sockets interface, and can also successfully mix the two interfaces within one application. What this provides, at the application level, is independence from the underlying network. In addition, because the BEA TUXEDO system networking libraries hide the specifics of a particular transport mechanism, other networking interfaces, such as X.25 or SPX/IPX, can be seamlessly introduced.
Distributed Transaction Processing (DTP)
The DTP capability of the BEA TUXEDO system guarantees the integrity of data accessed across several sites or managed by different database products. The BEA TUXEDO system coordinates distributed transactions to allow multi-site updates against heterogeneous databases on networked computers. The BEA TUXEDO system tracks transaction participants via the notion of a global transaction and supervises a two-phase commit protocol, ensuring that transaction commit and rollback are properly handled at each site. For instance, in a banking example of transferring money between accounts, a transaction will ensure that the debit to the "from" account won't happen unless the credit to the "to" account occurs, guaranteeing consistency.
The BEA TUXEDO system incorporates X/Open's TX interface for transaction demarcation. This interface allows an application writer to bracket a group of operations such that all of them will be done or none of them get done.
The BEA TUXEDO system also coordinates the recovery of global transactions in the event of site failure, network failure or global resource deadlocks. The BEA TUXEDO system uses the XA interface for communicating with the various resource managers. This interface was proposed by BEA TUXEDO to X/Open and has been accepted by X/Open as the standard interface for distributed transaction control between the transaction manager and resource managers.
Typed Buffers
BEA TUXEDO system applications communicating with one of the available API methods send and receive their data in typed buffers. Instead of allocating memory directly from the operating system, applications allocate typed buffers from the BEA TUXEDO system in which to place their data. Typed buffers are data structures defined by application designers and made known to the BEA TUXEDO system. Because the BEA TUXEDO system knows about the application data buffers, it can optimally manipulate them during communication. The BEA TUXEDO system provides several different kinds of typed buffers, but also allows application designers to define their own.
X/Open XA Compliance
The BEA TUXEDO system incorporates X/Open's XA Interface standard for coordinating transactions among multiple database managers participating in an application. The XA interface is part of X/Open's DTP model. Having this interface in the BEA TUXEDO system gives a customer the following benefits: