Behavior during backup
If a backup is started, the Data Manager carries out the following actions:
- It generates the input file for WCCOAtoolMedia
This file is located in the
<proj_path>/datadirectory and is called "input". - The Data Manager sets the status to "1" (backup is running), writes the buffer (cache) to disk and closes the database.
- The DataBG is stopped.
Note: This step (stopping the DataBG) is only relevant for RAIMA projects.
- All the current connects of managers are aborted if they require configs for initialization (this relates to drivers).
- All the current queries of historical values are aborted and answered with the message "Online backup of the database (#113)".
- The row "BACKUP" is written to the status line.
- WCCOAtoolMedia starts.
The following messages are answered with the error message "Error in the DM (#33):
Table: System Messages
| Message | Description |
|---|---|
| DP_MSG_SIMPLE_REQUEST | Retrieval of _archive config, dpGet() |
| DP_MSG_ASYNCH_REQUEST | Request for historical values, dpGetAsynch() |
| DP_MSG_PERIOD_REQUEST | Request for historical values, dpGetPeriod() |
| DP_MSG_ALERT_TIME_REQU | Request alarm time |
| DP_MSG_ALERT_PERIOD_REQU | Request historical alarms, alertGetPeriod() |
| DP_MSG_FILTER_REQUEST | SQL queries, dpQuery() |
| DP_MSG_CONNECT, DP_MSG_CONNECT_RET, DP_MSG_CONNECT_NOSOURCE | dpConnect() to _archive configs |
All other messages are placed in the message buffer. Beforehand, hotlinks are checked as to whether they relate to the DP Backup.Command and if they do, they are processed beforehand. For this reason, the Backup.Command DP should not be set together with a different DP as in this case, the order of archival of the last values will be changed.
This means that WinCC OA can also be operated in backup mode without data being lost. As in the emergency mode, queries that require an open database are answered with an error. All other messages are saved, however, and are processed after the backup mode has been left.
As no database accesses are possible in the time during which the Data Manager is in backup mode, no _archive configs can be displayed. Any alerts generated and acknowledged in this time, new, modified or deleted data points, data point types and configs will be processed after this time.
