Database Reference
In-Depth Information
21. To view information about agents, click the Agents tab.
22. Click the Warnings tab to configure alerts from pre-defined replication alerts. This
screen can be used to view information about agent warnings and thresholds.
23. Expand a Publisher group in the left pane, expand a Publisher, and then click
on publication.
24. Click the Warnings tab. Enable a warning by selecting the appropriate checkbox.
Warn if a subscription will expire within the threshold, or Warn if latency exceeds
the threshold.
25. Set a threshold for the warnings in the Threshold column. For example, if you have
selected Warn, if latency exceeds the threshold, you should select a latency of 60
seconds in the Threshold column.
26. Click Save Changes.
27. Again, Replication monitor gets the performance related values for replication.
The key values to monitor are: Current Average Performance and Current Worst
Performance columns.
The values are determined as follows:
For transactional replication, performance quality is determined by the
latency threshold. If the threshold is not set, a value is not displayed.
For merge replication, Replication Monitor displays detailed statistics for
each article processed during synchronization. Also the amount of time
spent in each processing phase (uploading changes, downloading changes,
and so on).
The key areas to lookup for replication performance tuning are:
latency, throughput, concurrency, duration of synchronization, and
resource consumption.
How it works...
All the data validations and monitoring aspects of replication are managed by the core
database engine. The validation works by calculating row count or checksum at the Publisher
and then comparing those values to the row count or checksum calculated at the Subscriber.
While the calculations are performed, shared locks are placed temporarily on tables for which
row counts or checksums are being run, but the calculations are completed quickly and the
shared locks removed, usually in a matter of seconds. When binary checksums are used, 32-
bit cyclic redundancy check (CRC) occurs on a column-by-column basis rather than a CRC on
the physical row on the data page.
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