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Oracle9i Architecture on Windows

This chapter describes how Oracle9i architecture takes advantage of some of the more advanced services in the Windows operating system.

This chapter contains these topics:

• Oracle9i on Windows Architecture

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Oracle9i on Windows Architecture

Oracle9i on Windows is a stable, reliable, and high performing system upon which to build applications. Each release of the database provides new platform-specific features above and beyond the generic database features for high performance on Windows.

Oracle9i operates the same way on Windows as it does on other platforms. The architecture offers several advantages on Windows, such as:

• Thread-Based Architecture

Thread-Based Architecture

The internal process architecture of the Oracle9i database is thread-based. Threads are objects within a process that run program instructions. Threads allow concurrent operations within a process so that a process can run different parts of its program simultaneously on different processors. A thread-based architecture provides the following advantages:

• Faster context switching

• Simpler System Global Area allocation routine, because it does not require the use of shared memory

• Faster spawning of new connections, because threads are created more quickly than processes

• Decreased memory usage, because threads share more data structures than processes

Internally, the code to implement the thread model is compact and separate from the main body of Oracle code. Exception handlers and routines track and de-allocate resources. They add robustness, with no downtime because of resource leaks or an ill-behaved program.

The Oracle9i database is not a typical Windows process. On Windows, an Oracle instance (the threads and memory structures) is a Windows service: a background process registered with the operating system. The service is started by Windows and requires no user interaction to start. This enables the database to open automatically at startup.

When running multiple Oracle instances on Windows, each instance runs its own Windows service with multiple component threads. Each thread may be required for the database to be available, or it may be optional and specific to certain platforms. Examples of optional and required threads on Windows are listed in Table 3-1.

Table 3-1  Required and Optional Oracle Threads

SQL> select * from v$bgprocess where paddr <> '00' ;

Figure 3-1 Oracle architecture on Windows. The background processes read and write from the various datafiles, depending on your configuration.

Text description of the illustration windows.gif

Oracle9i for Windows is supplied as a set of executables and dynamic link libraries (DLLs). Executable images can be modified using the ORASTACK utility to change the size of the stack used by the threads of the Oracle process. Oracle Corporation recommends you use this tool only under the guidance of Oracle Support Services.

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