An out-of-memory message can appear at any time, but you are most likely to run out of memory when working with a large number of objects or files, working with large images, and running multiple programs while you work. An out-of-memory message is often preceded by a noticeable dip in system performance. Here are a few things to try to maximize your use of your available memory:

Shut down any programs you don’t need. This is usually best done in the Windows Task Manager, displayed by using the <Ctrl>+<Alt>+<Del> key combination. Select the applications you want to close and then select End Task. The Processes tab can give you an idea of which programs are hogging the memory, but sometimes it can be hard to tell which process belongs to which application. You may end up shutting down something you want to keep running if you end processes indiscriminately. And sometimes the process you shut down will start itself right back up again.

Caption: Check the Mem Usage column to see what processes are consuming the most memory.

Set your system swap file size. When Windows runs out of RAM, it stores some of the overflow data in the swap file. If your computer is set to let Windows manage the swap file settings, the swap file size will adjust as needed to accommodate overflow data. If you have a static size set for the swap file, consider increasing the maximum size. Double-click on System in the Windows Control Panel and select the Advanced tab. Select the Settings button under Performance to display the Performance Options window.

Caption: Performance Options window is accessed via the Advanced tab in the Control Panel’s System Properties.

Under Virtual memory select the Change button to bring up the Virtual Memory dialog box. There you can adjust the size of the paging (swap) file.

Caption: Virtual Memory dialog box.

The swap file is stored on your hard drive. The more room you have on your hard drive, the more room the swap file has to grow. Consider deleting files or removing programs you don’t use if your hard drive is getting full. Start with temporary files and Internet cache files. Also look at program components you may not use. For example, if you’ve installed the AutoCAD 2011 Materials Libraries but don’t use them, consider uninstalling until you have a reason to use them. Note that you should make sure you have sufficient hard drive space before increasing the size of a static swap file.

Minimize drawing size. Take advantage of the many options AutoCAD provides for keeping drawing file sizes small. Unload the xrefs and images you don’t need. Change TrueType fonts to SHX ones. Break hatch areas into smaller sections. Use the Partial Open feature to view only that part of the drawing you are working on (see tip below for more details).

Get a new computer. If you consistently suffer from poor performance and out-of-memory errors, it may be time to retire your system and get a new one. If that is not possible, consider increasing your RAM. The more data that stays stored in RAM, the less that ends up in the swap file.

Setting the 3GB switch in Windows is another way to stave off the dreaded out-of-memory error message, but use with caution. Activating the 3GB switch can cause performance problems with some graphics cards that have onboard RAM.

Here’s how to set the switch in Windows Vista or 7 (we’ve covered Windows XP in the past):

In the Start menu, go to Accessories in the Program menu and right-click Command Prompt. Select Run as Administrator from the menu that appears. At the command prompt, enter:

• bcdedit /set IncreaseUserVa 3072

Restart your computer for the new setting to take effect.

Turn off the switch by opening Command Prompt as described above and entering:

• bcdedit /deletevalue IncreaseUserVa

Again, restart your computer for the change in setting to take effect.

Recently we discussed creating isometric drawings while in Isometric Snap mode in AutoCAD. When in Isometric Snap mode, you may find it helpful to enlarge your crosshairs to fill the drawing area. However, there may be a little bug with the CURSORSIZE system variable that keeps the crosshairs from extending to the edges when you set CURSORSIZE to its maximum value of 100.

Caption: Setting CURSORSIZE to 100 fails to produce the desired results.

The workaround is to set CURSORSIZE to 99 so that the crosshairs extend almost to the edges.

Caption: Setting CURSORSIZE to 99 gets us closer to the desired results.

Partialopen, a command that’s been around since AutoCAD 2000, allows you open only a specified portion of a drawing. To use Partialopen, select Open as usual from the File menu. Select your desired drawing file in the Select File dialog box, then select Partial Open.

Caption: Use the regular Open command if you haven’t used Partial Open on the drawing before. Once you select the drawing, you can select the Partial Open option.

The Partial Open dialog box appears. Here you specify a view to open (Extents is the default). Note that you can load only geometry from model space views saved in the drawing.

Caption: Select your view and layer geometry to load.

Next, select your desired layers. If you don’t select any layers, no layer geometry will be loaded, but all layer names will appear in the Layer Manager. Never draw on a layer that you haven’t loaded because you could be drawing on something.

Caption: Even if you don’t load the layer, all of them will be available in the drawing. You just won’t be able to see the geometry on layers you didn’t load.

Note that xref-dependent layers will appear in the selection list only if the drawing was last saved with VISRETAIN set to 1. Also note that any layers created in the xref since the xref was last loaded into the drawing will not appear in the selection list. You can opt to Unload All Xrefs on Open if you don’t want to load any xrefs contained in the drawing. One final xref note: If you partially open a drawing that contains a bound xref, only the portion of that xref that is loaded in your selected view will be bound to the partially open drawing.

If your drawing has a spatial index, select the Use Spatial Index option. This will help AutoCAD open the drawing more quickly.

When you’ve completed your selections, select Open. If you decide you need more of the drawing, select Partial Load from the File menu, or type Partiaload at the command prompt. This command is active only when the current drawing is a partially open one. In the Partial Load dialog box, select a view or choose Pick Window to define a view.

Caption: Running Partial Load from the File menu brings up a slightly different dialog box, which offers the option to use a window to define the view.

Save a partially opened drawing as you would a fully opened one. When you reopen a drawing that was saved in the Partial Open state, AutoCAD displays an alert message with options to Restore the partially opened state or Fully Open the drawing.

Caption: Alert message displays when you reopen a drawing that you saved when it was partially open.

Note that Partial Open works only with the AutoCAD format you're using. If you have AutoCAD 2010 and try Partial Open on an AutoCAD 2007 drawing, it won't work. Open and save the drawing in AutoCAD 2007 format, then run Partial Open.

Not to be confused with Partial Open is the OPENPARTIAL system variable, introduced in AutoCAD 2009. Think of OPENPARTIAL as Partial Open’s evil twin. When OPENPARTIAL is set to 1 (the default value), AutoCAD partially opens some drawings automatically—those that have been saved with paper space displayed and with the INDEXCTL system variable set to a nonzero value. It does this in order to speed things up when you open a large drawing—you can start working on the drawing before it is fully open.

Unfortunately, in the initial release of AutoCAD 2009, OPENPARTIAL came with a bug that could cause drawing corruption when you used the Purge command while a drawing was still opening. That issue was fixed in Service Pack 1.

You may still want to turn this capability off, however, because it can be somewhat disconcerting to open a drawing and find that some of its xrefs are missing (because they are still being loaded). Type OPENPARTIAL at the command line and change its value to 0. The variable is saved in the Registry, so changing it once should turn it off for all future drawings you open.