Re: InnoDB Buffer gets to 100% and doesn't go down

[Rick James]

> server buffer reaches 100%

What is the "server buffer"? If you mean InnoDB's buffer pool, then it is doing its job. It is a "cache"; it keeps "recently used" blocks in RAM for faster access. If it is completely full, then you have more data (120GB) than will fit, and it is busy making intellegent decisions as to which blocks to keep and which ones to flush out.

Let's see these:
SHOW VARIABLES;
SHOW GLOBAL STATUS;

Buried in the output from them will be information about how efficient the caches are being utilized.

You should be looking for slow queries, and seeing if they can be improved. Some slow queries will do "table scans", which flush the blocks out of the cache, thereby making them less useful. Others adversely impact the cache in other ways.