Physical Memory Usage

Although UNIX and D3 are virtual machines, they can run using a small amount of physical memory. The use of physical memory affects system performance. System performance can be considerably improved by increasing the amount of physical memory, so the processes do not frequently swap out to disk, a condition known as thrashing.

D3 and UNIX can also share memory resources to help alleviate this potential problem. However, the best way to avoid this performance bottleneck is to ensure that there is an adequate amount of physical memory.

This calculation is used to estimate the optimal amount of physical memory:

Physical memory = UNIX system memory + UNIX users

+ D3 monitor memory + D3 shared memory (core)

+ D3 FlashBASIC users (BASIC) + (UNIX-to-D3 users * 260 KB)

Parameter(s)

UNIX system memory	Memory required by the UNIX kernel and base system processes.
UNIX users	Amount of memory used for each UNIX user (such as users who do not log on to D3) running concurrently. This amount varies widely, so it cannot be fully taken into consideration here. Shared memory and physical memory requirements of the users must be determined as well as the physical memory requirements of the users. A good rule of thumb is to have at least 1 MB per UNIX user.
D3 monitor memory	Memory required by the D3 Monitor. Approximately 700KB (local data and stack).
D3 shared memory (core)	See Core Statement Calculations.
FlashBASIC users (BASIC)	See BASIC Statement Calculations.
UNIX-to-D3 users	Maximum number of users who log in to UNIX first, then execute D3. On D3 turnkey systems, D3 users bypass UNIX and log on to D3 directly, so this value would be zero.

Physical Memory Worksheet

Use this worksheet to calculate minimum physical memory requirements:

UNIX System Memory
	UNIX Kernel
	UNIX Users	_______	* 260 KB	______
Total UNIX System Memory					______
D3 Shared Memory
	D3 Monitor Memory			700 KB
	D3 Shared Memory (core)			_______
	D3 Shared Memory (BASIC)			_______
	UNIX to D3 Users	_______	* 260 KB	_______
Total D3 Shared Memory					________
TOTAL PHYSICAL MEMORY						________