Set memory and caching preferences by choosing Edit > Preferences > Memory & Cache (Windows) or After Effects > Preferences > Memory & Cache (Mac OS).

Maximum Memory Usage

Sets the maximum amount of memory to use for any purpose. You can specify values over 100% (where 100% equals the amount of physical RAM you have installed) because virtual memory uses hard-disk space. Values over 200% are not recommended. The default value is 120%.

Maximum RAM Cache Size

Sets the maximum amount of installed RAM to use for cached frames. If you set this value to greater than the default value of 60%, you may encounter problems such as decreased performance when switching from one application to another or increased frequency of errors that say that After Effects is unable to create an image buffer. Like a hard disk, your address space can become fragmented; if you have Maximum RAM Cache Size set too high, the memory may become too fragmented to store the next rendered frame. By lowering the cache percentage, you reduce the chance of fragmentation. Set this value above 60% only if necessary. You should not set this value above 90%.

When you have enabled multiprocessing, the amount of RAM available to background processes is affected by the amount of RAM reserved for the foreground process. Decreasing Maximum RAM Cache Size can free memory for background processes. (See Render multiple frames simultaneously.)

Enable Disk Cache

Moves rendered frames to your hard disk when the RAM cache is full. After Effects will only use the disk cache to store a frame if it’s faster to retrieve a frame from the cache than to re-render the frame. Select a folder to contain your cache, and click OK (Windows) or Choose (Mac OS). For the best performance, select a folder that’s on a different physical hard disk than your source footage. If possible, the folder should be on a hard disk that uses a different drive controller than the disk that contains your source footage. The disk cache folder can’t be the hard disk’s root folder.

Maximum Disk Cache Size

Specifies the number of megabytes of hard disk space to use. This should be at least 2 gigabytes (GB).

Prevent DLL Address Space Fragmentation

Select this option to give After Effects access to more contiguous memory on a computer with a large amount of RAM. This option may be incompatible with some OpenGL drivers, which can cause a crash when the application starts. If a crash occurs, the option will become unchecked automatically to prevent further crashes when you start After Effects.