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Last tested: Jan 24, 2021
When we use system activity in Looker, we’re directly querying the tables stored in the internal database. Because Looker is constantly reading from and writing to the internal database, if we allowed users to query the tables without restriction on top of this, performance issues would certainly ensue. That’s why we limit the number of concurrent queries to 1 for the internal db; that is, we only allow one System Activity query to run at a time. If you try to run concurrent queries, additional queries will be queued until the first completes.
Another way we attempt to keep from overloading the internal db is by only updating and caching the data in System Activity dashboards every 12 hours.
Instances that use Elite System Activity use more robust methods of improving internal DB performance, and because of this, the 1 query concurrency limit and 12 hour caching policy for SA dashboards aren’t imposed.