Cisco Cisco IPCC Web Option User Guide

Historical data is stored in the ICM Logger's central database and in the Historical Data Server (HDS)
on the Distributor Admin Workstation. You must use the HDS if you want to use WebView for reporting.
Using the Logger's central database for reporting with WebView is not supported.

Typically, you set up two Distributor Admin Workstations as HDS machines. The same fault-tolerant
strategy that applies to the real-time Distributor AW also applies to the HDS; that is, when the primary
HDS fails, the Client Admin Workstation automatically switch over to use the backup HDS.

Each Historical Data Server (HDS) is connected to a single Logger. The Logger's central database
replicates historical data to the HDS. The replication process may have a latency of about one to five
minutes because the Logger replicates data table-by-table on the HDS.

You configure the number of days for which data is stored in the Logger central database and the HDS.
The Logger stores data for less time than the HDS. For example, you might store two weeks of data on
the Logger and a year of data on the HDS. You should configure the amount of time that data is stored
on the Logger in relation to the schedule for HDS backups to ensure that you do not lose data in the event
that the HDS goes offline. When the HDS recovers after going offline, it retrieves all data from its most
recent backup and all of the data on the Logger for the interval for which data is missing from the backup.
For example, if the HDS backup has data up to the last two weeks, the HDS would replicate the last two
weeks of data from the Logger when recovering. The amount of data retained on the Logger should cover,
at a minimum, the time period between HDS backups. For example, if the Logger stores data for two
weeks, then you need to back up at least every other week to ensure that you can recover all historical
data.

If the Logger connected to the HDS goes offline, the HDS does not connect to a different Logger. For
example, if the HDS is connected to Logger B, it does not connect to Logger A if Logger B fails. When
Logger B comes back up, it recovers data from Logger A and begins to receive current historical
information. Once the Logger has recovered all of the data from Logger A, it begins to replicate this data
to the HDS. If reports are run from this HDS for recent intervals while the Logger is offline, or while the
Logger is in the process of recovering or replicating data, you might not see data for those intervals in
reports. This is temporary and you will see the data once the replication process for the tables utilized by
the reports is complete. If you are using a fault-tolerant system with two HDS Distributor Admin
Workstations, you can run reports using the backup HDS while the primary HDS is not receiving data

If the HDS goes offline and you are using a fault-tolerant system with two HDS Distributor Admin
Workstations, you can run reports using the backup HDS. When the HDS comes back up, it recovers
data from the last HDS data backup. It also replicates data from the Logger for the most recent data not
available in the backup. The recovery data replication is faster than regular Logger-HDS data replication.
Once the HDS has recovered to its typical Logger-HDS latency of one to 5 minutes, data replication
proceeds as usual. If you are not using a fault-tolerant system, you will not see data in historical reports
until the HDS is restored. You might also notice missing data as the replication process is in progress.
This is temporary and you will see the data once the replication process for the tables utilized by the
reports is complete.