The Shared-Memory Component

Shared memory is an operating-system feature that lets the database server processes and threads share data by sharing access to pools of memory. The database server uses shared memory for the following purposes:

• To reduce memory use and disk I/O
• To perform high-speed communication between processes
• To enable virtual processors and utilities to share data

The database server creates the following portions of shared memory:

• Resident

  Caches data from the disk for faster access

• Virtual

  Maintains and controls the resources required by the virtual processors

• Interprocess (IPC) communications

  Provide a fast communications channel for local client applications that use IPC communication on UNIX

• Virtual extension

  Enables DataBlade modules and user-defined routines (UDRs) to run in user-defined virtual processors