RDB Archiving
RDB archiving by means of a specially designed RDB Archive Manager allows archiving values and alerts in a relational database (hence the name RDB = Relational Data Base). You can read this data either from WinCC OA or by means of external tools that allow querying the Oracle database.
The type of archive is not important with regard to the core processes of WinCC OA (event and database manager, drivers and user interface). The various types of archive are transparent for these processes and you can use the same tools to save and query the values. For further information on the default archive system used by the WinCC OA Value Archive, see the chapter History DB.
The current implementation of the RDB Archive Manager has been specially designed for Oracle databases. The RDB archiving concept also allows saving values and alerts, no matter what relational database they are stored in. The design of the RDB Archive Manager is flexible in this respect. At present only the relational database of the company Oracle (standard or enterprise edition) can be used.
The entry "useRDBArchive" in the config file determines whether the RDB Manager will be used to archive data in WinCC OA.
Inside the RDB event messages are only stored in the default language.
When archiving multi-language texts (data points of type langString) only the current language of the data manager is archived.
You can evaluate the data in the relational database not only with the on-board WinCC OA tools (for example, alert and event screen, control queries) but also with specialized third party query tools (You can also query the Oracle DB directly from Excel). Further points of interest include the Oracle features "Data Guard" and "Real Application Cluster" that are also available for the archives in a WinCC OA project.
The Oracle database, similar to the value archives, holds archive sets of variable size and switching times. Similar to the Value Archives, you can also specify the number of completed archive sets and their backup time (see Creating archives and setting parameters in the History DB). Archive sets that have already been backed up can be restored and are then available again for evaluations.
As indication for needed storage space following values can be used: A value change for event-logging needs approximately a size of 120 Bytes while a value change for alarm-logging needs approximately a size of 400 Bytes. These indications are without commitment and a fluctuation of needed storage space can occur.
Note the following for the time values and variables:
- Runtime values/alarms can be created with an accuracy of up to nanoseconds.
- Historical databases retain the correct sequence, but only store up to milliseconds, i.e. they discard the parts with higher accuracy.
- The comparison of WinCC OA time variables only takes milliseconds into account. WinCC OA time variables that only differ in the microsecond or nanosecond range would be considered the same by the built-in comparison methods.
Communication between WinCC OA and Oracle (read and write values, change archive sets and others) is performed with special DLLs that use the Oracle API interface. This communication is also based on TCP/IP, similar to communication between the individual WinCC OA managers. An important issue is that a connection (in case of Oracle via Oracle*Net) to the database has to exist on the computer which is used to access the relational database (WinCC OA server or also a remote work station).
In order to take the load off the RDB Archive Manager for read operations on the Oracle database, a special add-on has been developed that allows direct Oracle queries from a control script using special CONTROL commands (see Direct read functions) without having to go through the RDB Archive Manager. A special entry in the config file causes all history queries in WinCC OA (trend, alert and event screen and others) automatically to be sent to the relational database directly through the CONTROL DLL and not forwarded via the Data Manager and RDB Archive Manager. This is faster but only returns archived values (for value queries) as opposed to recent values of DPEs that have not been archived.
The installation scripts setup WinCC OA access to Oracle and also create the tables required for archiving. In order to further simplify matters, there are already several views that allow faster and easier evaluation of these (archive) tables using third party tools.
When using RDB Archiving the config "_alert_hdl..help" can not be queried.
Connection Pooling in the Reporting Manager
Connection pooling enables the use of several database connections (maximum of NofConnections) simultaneously. Until now all the RDB queries sent to the Reporting manager were processed successively via the same database connection. By using the connection pooling, several queries can be sent simultaneously to the database. Via the connection pooling specific config entries you specify, for example, how many reporting queries are processed simultaneously. See the new config entries:
IncNofConnections
NofThreads
NofConnections
MinNofConnections
in the [reporting] section of the config file.
| Chapter | Description |
| RDB archiving, basics | Introduction and links to the other chapters |
| Requirements and Installation | System requirements for installation of RDB archiving |
| Functionality of the RDB archiving | Explanation of how RDB archiving works in WinCC OA |
| Configuration of the RDB Archive Manager | Description of the panel used to set parameters for archiving data from WinCC OA to a relational database |
| Setting archive group parameters | Description of the panels for configuring the archive groups |
| RDB archiving parameters | Description of the panels for configuring the archiving of data point elements in the module PARA |
| Example for a RDB query | Step-by-step instructions for a query with Excel into the RDB |
| User defined archive groups | Until now the archive tables in the WinCC OA database had a fixed structure. A table always comprised the same specific columns. Using the user defined archive groups you are no longer restricted to a fixed structure but you can create your own archive groups. |
| Possible config entries for RDB archiving | Description of config entries for RDB archiving |
| Redundancy | Information about the replication of the active and the passive RDB manager. |
| Data buffering, basics | Data buffering provides the protection against data loss, thus data are buffered in addition to RAM also on the hard drive disc. |
| Starting the RDB manager without DB connection | Description of the BufferToDisk functionality process while starting the RDB manager without database connection. |
| Direct read functions | Details for advanced WinCC OA users to direct read functions into the RDB |
| Historical Synchronization | Description of the historical synchronization between the subsystem and the central system. |
| Description of tables and views | Details for advanced WinCC OA users to tables and views in the RDB |
| Troubleshooting | Description of the two diagnostics scripts for troubleshooting reasons in RDB. |
| Summary and relevant links | Links to other relevant chapters in the Online Help |
