Hit Ratios Help
Hitratios are a very way to get a big picture of how well your database is performing. Essentially a hitratio gives you a ratio with which to quickly judge how many I/O requests are being satisfied via memory vs I/O requests which actually require disk I/O.

We monitor data block buffer hitratio, dictionary cache hitratio and so on. Configure hitratio monitoring as follows:

hitratios:5:95:70

In this example we're checking every 5 minutes. If the hitratio is below 95%, we're at WARNING level, and if it drops below 70%, we're at ALERT level.