In case a red hexagon or yellow triangle appears beside a metric, it means that the current value of the metric exceeds the set threshold value, ie., the symbols signify alert conditions. The definition of what should trigger a red hexagon or yellow triangle alert is defined in the JavaScript component defining every metric. The default values that SQL DM for MySQL ships with have been configured for average servers used for mixed purposes: a mix of websites and databases with corporate data, for example.
You may want to change the values depending on the type of databases. Threshold values for the metrics (and also actual, realizable, values) varies depending, at the very least, on the type of applications that use the database. For instance with certain web applications like Forums a very high 'cache hit rate' typically can be reached (as a large percentage of queries return the most popular post in the Forums) whereas in a production planning system it is typically not possible to achieve a very high hit rate (as identical queries and results only rarely occur here).
Red and Yellow alerts will quickly tell what could be issues to investigate.
