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Message Posted: Thu, 26 Mar 2015 @ 23:27:37 GMT
Canary queries are used as the basis for alert mechanisms to know the state of the system but you need to know what you want to measure. Generally they are divided into two categories:
o) Check specifically for entire database hung or slowed down
o) Concurrently, capture information from every node about AMP worker tasks, message queues, scheduler allocation, etc.
o) Design canaries so they are never intrusive
Ex. Select * from dbc.dbcinfo; - an all-AMP, subsecond query
o) Check consistency of response for highest priority or shortest expected responses
o) Check consistency of response within a particular allocation group
o) Query is reflective of the typical workload
In either case, you will want to track/chart canary response against other conditions such as # Sessions, # AMP worker tasks in use and % CPU busy.
Hope this helps.
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