The Database Availability statistics show an aggregate of availability statistics, generated by the MySQL Availability Advisor, for all MySQL Instances within the selected group, and allows you to monitor your availability.
The MySQL Availability Advisor must be enabled for this functionality to work. It is enabled by default.
Database Availability is computed by each MySQL Enterprise Monitor Agent attempting a connection to the monitored MySQL instances (by default every 1 second, but this is configurable within the Advisor), to check whether the MySQL Instance is actively accepting new connections.
To see a summary of the instance availability per period, hover the cursor over any of the availability bars to display the Availability pop-up. The availability is broken down in to four categories:
Available: The percentage of time the monitored instances were actively monitored.
Up: The instance
Uptimereports the percentage of time the instance was running but was not monitored.
Unreachable: The percentage of time a monitored MySQL Instance did not respond.
Down: The Agent could not get a response from the MySQL Instance at all.
For each time range, the bar chart is split up in to slices of time (1 or 2 pixels each, depending on the width of the display), which represent a period of time; Day = 4 minutes, Week = 20 minutes and Month = 2 hours. Within those slices, the time within each availability state is aggregated across all MySQL Instances within the selected Group, and shown as the percentage of the total time in the slice.
For example, if you have four MySQL Instances within the selected group, with three of them being up and one of them being down for a 4 minute period within the day, the slice representing those 4 minutes would be 75% dark green, and 25% red.
This graph is not displayed for any selection from the All Targets menu, except the MySQL instances.