Database Reference
In-Depth Information
LRT
Synchronous read
2012 × 9 ms = 18 s
21 s
Indexes:
Tables:
17
1995
SQL
Non -SQL
20 s
1 s
1 s
18 s
1 s
0 s
0 s
Wait for
prefetch
CPU time
Sync
read
Lock
waits
Other
waits
Figure 7.1 A spike example.
LRT
Service
Queuing
Long service time
Long queuing time
CULPRIT
VICTIM
Figure 7.2 Culprits and victims.
to carefully prioritize the modules analyzed; the transaction response times and
frequencies are not the only criteria.
The first distinction we should make is that between the culprit and the
victim , as shown in Figure 7.2. If a transaction monopolizes resources, perhaps
because of inadequate indexing, it will obviously have an adverse effect on
other transactions, and so these will consequently appear on the exception report
together with the culprit.
The resources used by the culprit will be included in the service time; the
victim will be affected by having to wait for the resources, namely the queu-
ing time.
It is logical to begin the tuning process by addressing the problems caused
by the culprit rather than the victim.
 
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