RDB Compression

In addition to the WinCC OA compression also RDB compression is supported. RDB compression means that the Oracle database is able to calculate the compressions on its own, provided that for archiving of values a relational database (RDB) is used.

Generally, compression is used in order to minimize a large amount of historical data. For instance, only daily or weekly averages are of interest after a certain period of time. In this case, average values are archived, for example, first hourly, then weekly or monthly averages are calculated from these and archived. This makes it easier to obtain an overall picture of the data.

The user does not intervene directly in the database. All actions are launched from WinCC OA and the Oracle RDB database returns the requested information. Once a compression has been added to a data point element, the compression calculation can be started in defined intervals.

The RDB compression has to advantages compared to the WinCC OA compression:

  1. The compression takes place on the basis of a complete data amount (whereas an initialization of interim values is not necessary during project start).

  2. The compression is not calculated in the Event Manager (faster setup, less computer load, lower hard disc usage).

  3. For the RDB compression no any additional data point elements are needed, as the compressions are defined as a property of the already existing data point elements.

Functionalities

The following functionalities are provided by the RDB compression:

  • Creating / Activating / Deletingcompression intervals for the RDB compression. A compression interval defines the interval in which there is a compression calculation of the values of a data point element (e.g. 5 minutes, 1 day, etc.).

  • Creating / Activating / Deleting compression steps. A compression step defines the composition of an interval with an arithmetic function. The following compression functions are provided (for details see functions).

    • Sum (SUM)

    • Minimum (MIN)

    • Maximum (MAX)

    • Arithmetic average (AVG)

    • Integral average (AVG_INTEGRAL)

    • Difference (DIFF)

    • Difference absolute (DIFFABS)

    • Minimum with time (MIN_TIME)

    • Maximum with time (MAX_TIME)

  • Creating / Activating / Deletingcompression calculations for data point elements, which are known only in the database but not in the WinCC OA DP identification, whereby "virtual data point attributes" are generated.

  • Hierarchical relations of compared data point elements (an RDB compression can be based upon another).

  • Adapting compression calculations that have been configured for the data point elements of a master data point to all data points of the corresponding data point type (mass configuration).

  • Import and Export of an RDB compression configuration using an individual ASCII panel.

  • Cyclic calculation of compressions and storage of the results in the relational database.

  • Querying available compressed data point elements ("DP-Selector").

  • Access to compressed data point element values in the WinCC OA Trend.

  • Access to compressed data point element values in the WinCC OA event screen.

  • Synchronization during RDB startup

    During the startup of the RDB Manager changes in the DP identification (e.g. deleting data point elements or removing the _archive config) have effects on the data point elements compressed in the RDB (compression calculations). These changes are updated automatically, i.e. the state of the data point elements is updated from WinCC OA to RDB.

  • Deleting RDB compressions at runtime

    Even if WinCC OA is running re-configurations in WinCC OA (e.g. deleting data point elements or removing the_archiveconfig) have effects on the RDB compression calculation stored in RDB. These changes are updated automatically.

  • Synchronization via Disaster Recovery System

    For online values and alarms it is possible to perform a synchronization with the redundant stand-by database using a special database link. Thereby it is also possible to copy compression intervals, steps and calculations from the active database to the stand-by database. The calculation takes place in the database.

When using RDB compression, correction values are not supported by WinCC OA version 3.20.

Dynamic Behavior

C. - Compression

The user does not access the database directly. All actions are started from WinCC OA and the Oracle RDB database delivers the needed information. As soon as an interval is available the cyclic interval calculation starts for this interval.

Chapter Overview

Chapter Description
Basics on RDB Compression Basic information on RDB compression and its functionalities.
Installation and Requirements - RDB Compr Requirements and installation of the RDB compression.
Configuration
Configuration - Introduction Introduction on configuration of the RDB compression.
Configuration of Compression Intervals Basic information in compression intervals and instructions on how to create, edit and delete a compression interval.
Configuration of Compression Steps Basic information in compression steps and instructions on how to create, edit and delete a compression steps .
Allocating Compression Calculations to Data point Elements Basic information in compression calculations and instructions on how to allocate, edit and delete compression calculations to/of data point elements.
Mass Configuration of multiple Data Point Elements Instruction on allocation of compression calculations to multiple data point elements of a data point type with master data point.
ASCII Import and Export of a RDB Compression Configuration Description of the ASCII import and export panel for importing and exporting an RDB compression configuration.
Trend Display of compressed Data Point Elements Instruction on how to display compressed values in the trend.
Display of Compressed Values in the Event Screen Example of displaying compressed values in the WinCC OA event screen.
Description of the Tables and Views Description on the Tables and Views in the database that have been created due to the RDB compression.
Details on RDB Compression Information on reading RDB compressed values and Oracle jobs.
Notes and Restrictions Notes and Restrictions regarding the use of the RDB compression.