While performing some actions AECOsim runs out of memory and the About AECOsim Building Designer dialog shows something like this:
To do this operation you will need the Administrator Credentials to the computer. Once you log in to the computer with Administrator Credentials, follow the following workflow:
This will add the user for Locking pages in memory. A restart is required for the setting to get applied. Once a restart is done, the memory issue will no longer appear.
MicroStation Memory Management