Clear CPU, GPU, or RENDER memory. Available to super users only.
ALTER SYSTEM CLEAR (CPU|GPU|RENDER) MEMORY
Examples
ALTER SYSTEM CLEAR CPU MEMORY
ALTER SYSTEM CLEAR GPU MEMORY
ALTER SYSTEM CLEAR RENDER MEMORY
Generally, the server handles memory management, and you do not need to use this command. If you are having unexpected memory issues, try clearing the memory to see if performance improves.