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Memory Management and Local Area Networks

Article excerpt

Over the past few years, desk. top computing environments have steadily moved from that of stand alone PCs to networked PCs. There are many advantages to this new, distributed computing environment. The network gives us the ability to share resources such as data and printers, and to communicate with others within the organization. If our network is connected to the Internet, global communication and resource sharing become possible.

While the benefits may seem apparent, some of the many costs of a networked environment are not so obvious. For instance, training users can have a significant cost but is an essential component to a smooth, productive transition to this new operating environment. In addition, there is the cost of upgrading the individual PCs by adding additional random access memory (RAM) and additional disk storage that may be needed to support the connection to the network.

While effective PC memory management is a desirable goal for a stand alone PC, it is absolute critical for PCs connected to a network. We would now like to turn our attention to some of the experiences we had in dealing with the limitations of DOS memory and discuss the implications that these limitations had in a Novell network environment.

OUR OPERATING ENVIRONMENT

We maintain a small instruction computer center with a relatively small LAN of nineteen PCs connected to a 486 file server running Novell NetWare 3.11. Most of our PCs are 486 machines with either 8 or 16 megabytes of RAM and are running DOS versions 5.0 through 6.2. In addition, many of these networked PCs have local CD-ROM drives attached to support databases or multimedia products. Our LAN is also connected to a wide area campus ethernet that is our gateway to the Internet and other campus resources. We run virus protection on all our machines and also run a menu program produced by Saber Software that provides access to the programs on the network.

On a beautiful fall day last October, we finished connecting our last PC to the new server. A menu was created that included an option to run CD-ROM programs if a CD-ROM player was connected to that machine. While testing each menu option, we discovered that, while most of our Windows based programs were working fine, our CD-ROM programs were not. Both the Bowker's Children's Reference Plus 6.1 and the Wilson Library Literature 2.5 were giving insufficient memory errors now that the PCs were connected to the network. Both of these machines had 8 MB of RAM--how could we not have enough memory? The programs require only 539 and 475KB respectively, of conventional memory. When we looked at the amount of memory available using the MEM command, we were shocked to learn that there were only 424KB (388.1KB if our network menu program was not exited) available in conventional memory for DOS programs. It looked like a good time to get a little more serious about memory management.

MEMORY USE IN THE NETWORKED PC

Table 1 shows what and where the DOS operating system was loading on boot up before the machine was networked.(Table 1 omitted) Even before the network software was loaded, we needed to improve our memory management because the external CD-ROM player requires a device driver, the Microsoft CD-ROM extensions program, and the SETVER program (needed because MSCDEX does not know about versions of DOS later than 4.01). In addition, memory is used by the command interpreter and the mouse program.

All these programs were currently using conventional memory and we have 525.1KB available for other programs. This is enough memory to run Wilsondisc 2.5; the Bowker CD-ROM product will run but could have problems at this level. Additional RAM is made available by unloading our Norton Antivirus TSR when that CD-ROM program is used.

To connect to the network, several initial configuration changes must be made. For instance, a LASTDRIVE statement in CONFIG.SYS must reflect the last drive letter to be assigned to the PC and the SHARE. …