so I have enabled query caching on my server but now from the 8 GB RAM there is almost non left! CPU is around 3% !
Now what happens when there is no more RAM left?
Will this just increase CPU load?
If no more RAM is left and the server still needs more memory, it will start swapping if not already started. When no more RAM or swap is available, the server will crash. Generally, the CPU load may increase as a result of the more required processing and degraded performance.
The best thing to do is trying to determine the reason for this. You need to check which processes are using more memory.
if a server starts swapping, it discards the oldest values or whatever there is policy regarding eviction of stored query cache..query caching is transient type of store.