Walkthrough
You have access to the following categories of
data:
Waits. Wait – is a time, SQL
server spent on waiting latches or CPU. Waits are groups in
the following categories:
-
CPU – SQL server was calculating something.
-
Writes - SQL server was writing for the IO system
-
Reads – the same for reads
-
Locks – SQL server was waiting for the data-level locks (except some
artificial locks, like a command WAITFOR DELAY, only ‘bad’ locks, when one
process is waiting for another are counted)
-
Network – SQL server was waiting for the response from a network.
The important note is that CPU is different
from the CPU recorded in the PerfMon. In fact, your waits can
consist mostly of the CPU, while the CPU is TaskManager or PerfMon
can be very low. How is it possible?
Imagine SQL server idling most of
the time. Once an hour, SQL server receives a request, which
requires a lot of CPU power. SQL server is calculating the result
for 1 minute, and replies to a client. The CPU will be 1.6% (1
minute per hour CPU is busy), but or diagram will indicate, that
waits mostly consist of the CPU
So we count only the events,
important for a DBA.
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