Source Insight uses about 16 bytes of RAM for every symbol index entry in a project. A project with all the symbol index options enabled (see “Project Settings”) will use about 5 or 6 times as many index entries as there are symbol definitions. Therefore, for example, if your project has about 100,000 symbol definitions, then it will have about 500,000 index entries. That will take about 16 x 500,000 = 8,000,000 bytes to hold the index.