Notes and Restrictions

Third distributed system

You can connect to a Disaster Recovery System with a third distributed system. However, no data or files are synchronized to this third system.

System names

When the system name of a redundancy pair (PSS or SSS respectively) is used (e.g.: data point groups, AES configurations, etc.), these settings will not work for the second redundancy pair. Therefore, all settings that affect the Disaster Recovery Systems must be made without system names.

Failure of a redundancy pair in a distributed system

A distributed system on the Disaster Recovery redundancy can only use data of one redundancy pair. If the redundancy pair fails, the data of the second redundancy pair is not automatically used, as the second redundancy pair has a different system name.

Deleting data point configs

The synchronization of the configuration does not include the deletion of data point configs. Instead of deleting a data point config, it should be deactivated. If, for some reason, this is not possible (e.g. data point functions), it should be deleted manually on both of the systems (PSS and SSS).

Alert colors and levels after the reconnection of a system

When a system is reconnected after a total failure, analog data points with alert handling may have different alert colors or alert levels on the PSS and the SSS. This could be the case, for example, if an analog value has an alert class with three alert levels (e.g., alert, warning, and no message) and the data point value exceeds the highest level limit, triggers the alert, and then exceeds the limit again while the system is still in a state of failure. The failed system now goes back into operation, the alert of the system is set to warning only, while the alert of the other system remains an alert, since the system cannot detect that the alert limit has been exceeded. However, after the alert is acknowledged, both systems again display the same alert status.

Multi-instance alerts

Since the configuration synchronization is not supported for multi-instance alerts, data points must be manually configured on both systems.
For SELECT ALERT SINGLE (alert leading to last alert handling (for dpQueryConnectSingle()), acknowledging is not transferred. See also Example of setting alert handling for multi-instance alerts using CTRL function calls.

Synchronization of historical data after disconnection

The synchronization of historical data (e.g. after an interruption of the connection between PSS and SSS or a system failure of the SSS) is not performed automatically, but must be activated by the user in the corresponding panel.

Error message after an alert was acknowledged

If an alert is acknowledged by the automatic synchronization function of the Disaster Recovery System (e.g. synchronization of PSS and SSS), a warning message is output in the log viewer. However, this warning message has no negative impact and can therefore be safely ignored. For example:

 WCCILevent (0),
 2008.05.21 10:11:17.616, PARAM,WARNING, 23, Setting/modifying attributes failed,
 DP: System2:dp:_alert_hdl.._ack, MAN: (SYS: 1 Ctrl -num 4 CONN:1)

RDB compression configuration synchronization

The configuration synchronization of the RDB compression configuration is only possible via the ASCII Import/Export panel of the RDB compression (see ASCII Import and Export of an RDB Compression Configuration).

Synchronization of internal data points

Internal data points are not synchronized by default. If synchronization is required, the appropriate settings must be made using the configuration wizard.

Synchronization of Alert Comments

Comments in a DSR system are synchronized as follows:

Comments are synchronized from the active to the passive system. Alert comments are synchronized only if the alert status is synchronized.
Comments are not synchronized form the passive to the active system.
If the passive system is temporarily unavailable while a comment is entered in the active system, the comments will be synchronized when the passive system becomes available again.
A historical alert can also be commented on.

Limitations

Alert comments are only transferred if the alerts are identical.
Alert comments are synchronized historically.
If there is no connection between the DRS partners, an alert comment could be lost since the data on the PSS (Primary Server System) is synchronized with the current data on the SSS (Secondary Server System).
Synchronization direction (active -> passive) is identical to the synchronization direction of the alert statuses (acknowledgements).
If you need the autologin functionality in the DRS, you must implement your own disRecSystem_client_RenewDRSAutoLogin function. If you have modified the distRecSystem_client.ctl in your project, you must upgrade from 3.17 to a higher version or merge the changes into your current version script since the included login_internal.ctc does not exist in 3.17.