Dynamic Scalable Architecture

Informix database servers implement an advanced architecture that called Dynamic Scalable Architecture (DSA). DSA provides distinct performance advantages for both single-processor and symmetric multiprocessor computers. These advantages, which this section describes further, are as follows:

• A small number of database server processes can service a large number of client application processes, with the following benefits:
  • Reduced operating-system overhead (fewer processes to run)
  • Reduced overall memory requirements
  • Reduced contention for resources within the database management system (DBMS)
• DSA provides more control over setting priorities and scheduling database tasks than the operating system does.

Parallel-Processing Architecture

The multithreaded database server exploits symmetric multiprocessor (SMP) and uniprocessor architectures.

DSA particularly exploits SMP and massively parallel processing (MPP) computer systems. DSA provides the following additional benefits on those systems:

• Multiple processes can work in parallel for one client.
• On some multiprocessor computers, you can bind database server processes to specific CPUs.

Figure 1 shows the three major components of the Informix database server architecture.

Figure 1. Database Server Architecture Components

Informix database server architecture includes the following the three major components:

• Virtual processors

  A virtual processor is a task that the operating system schedules for execution on the CPU. A database server thread is a task that the virtual processor schedules internally for processing. Database server virtual processors are multithreaded because they run multiple concurrent threads. For more information, refer to Virtual Processors and Threads.

• Shared memory

  Shared memory consists of a resident and virtual portion. The database server uses the resident portion to cache data from the disk for faster access by multiple client applications. The database server uses the virtual portion to maintain and control the resources that virtual processors require and to read in large blocks of infrequently accessed data. For more information on how the database server uses shared memory, see Shared Memory, and Managing Shared Memory.

• Disk component

  The disk component is a collection of one or more units of disk space assigned to the database server. All the data in the databases and all the system information necessary to maintain the database server system reside within the disk component. For more information on the disk components, see Data Storage.

The multithreaded database server manages access to one or more relational databases for client applications. In a relational database, data is organized in tables that consist of rows and columns.

Scalability

DSA allows the database server to scale its resources to the demands that applications place on it. A key element of DSA is the virtual processors that manage central processing, disk I/O, and networking functions in parallel.

For more information on virtual processors, refer to Virtual Processors. To understand how the database server manages shared memory to scale performance, see Shared Memory. For tuning and performance information, refer to your IBM Informix: Performance Guide.