When you insert an image using the Insert An Image command, AutoCAD Map 3D stores information about the image in the drawing, loads the image into memory, displays it onscreen, and locks the image file on the disk.
You can increase redrawing speed by hiding or unloading images you do not need in the current drawing session. Hidden images are not displayed or plotted; only their drawing boundaries are displayed. You can choose to hide an image regardless of the current viewport coordinate system. If you no longer need the image in the drawing, you can erase a single instance of the image or you can detach the image to erase all instances of the image and the image information.