If the Database load (DB load) chart shows a bottleneck, you can find out where the load is coming from. To do so, look at the top load items table below the Database load chart. Choose a particular item, like a query or an application, to drill down into that item and see details about it.
DB load grouped by waits and top queries typically provides the most insight into performance issues. DB load grouped by waits shows if there are any resource or concurrency bottlenecks in the database. In this case, the Top queries tab of the top load items table shows which queries are driving that load.
Your typical workflow for diagnosing performance issues is as follows:
-
Review the Database load chart and see if there are any incidents of database load exceeding the Max CPU line.
-
If there is, look at the Database load chart and identify which wait state or states are primarily responsible.
-
Identify the digest queries causing the load by seeing which of the queries the Top queries tab on the top load items table are contributing most to those wait states. You can identify these by the Load by Wait (AAS) column.
-
Choose one of these digest queries in the Top queries tab to expand it and see the child queries that it is composed of.
You can also see which hosts or applications are contributing the most load by
selecting Top hosts or Top
applications, respectively. Application names are specified in the
connection string to the Amazon DocumentDB instance. Unknown indicates that the
application field was not specified.
For example, in the following dashboard, CPU waits account for most of the DB load. Selecting the top query under Top queries will scope the Database load chart to focus on the most load that is being contributed by the select query.
