How UNIX Manages Memory

The UNIX operating system is responsible for allocating sufficient memory resources for all processes running on the system. UNIX operating systems allocate three separate areas in memory for each process.

Text Segment

The text segment ontains machine-level instructions for the program or process's operation. These instructions can be used by multiple processes without loading individual copies of the code if the code is written to be reentrant. Such reentrant code is code that is written to resolve multiuser conflicts caused by several processes calling the shared code simultaneously.

Programs running under UNIX use shared text segments and therefore share code. This greatly cuts down on memory requirements, as multiple client processes can access the same code without having multiple copies of the code in memory. Multiple server programs also share common code.

Data Segment

The data segment contains global variables, buffers, and other data structures to be accessed by the process. These data segments are private to each sqlturbo.

Stack Space

The stack space ontains internal storage for individual processes. Largely invisible to the user. OnLine processes maintain individual stack spaces and these areas of memory are not shared.