Starting a Monitor
When a monitor is running, the plugin intercepts WordPress’s queries to your database, including queries from plugins like WooCommerce, BuddyPress, and others. It measures how long each query takes, and then looks up what indexes, if any, the query used. It accumlates the queries into a saved monitor that you can view later.
You can give each monitor its own name, and you can capture only one monitor at a time.
When you know certain operations on your site are too slow, start a monitor and then perform those operations while the monitor is running. For example, it make take too long to search for a product in a WooCommerce site. To isolate the slow database query or queries causing the slowdown, start the monitor and then search for that product.
You can also start a monitor during a busy time of day on your site, and let it monitor your users’ operations for a few minutes. When you view the monitor you will see the slowest queries.
Choosing operations to monitor
Each pageview generates many queries to your database. Once a pageview is chosen, randomly, to be part of the sample, the plugin monitors all queries for that pageview.
You should delete a monitor before starting a new one with the same name. If you don’t the plugin will resume capturing into the existing monitor.