You can change the Symantec endpoint client file cache settings by follows this procedure:

1. Open the Symantec endpoint protection client.
2. Go to > change settings.
3. Press "configure settings" under "Antivirus and antispy protection".
4. Go to "file system auto protect" and press "advanced".
5. Under "file cache" change the setting you want.
Important to know: it is not recommended to change those settings, but some solutions or 3th
party tools  requires disabling the file cache.
Anyway, you can also change the cache size and decide whether to rescan the cache when a new definition loaded.