Introduction and comparison of real-time databases

Real-time database is a branch of the development of database system, it is suitable for dealing with the rapidly changing data and time-limited transaction processing. Real-time database technology is a combination of real-time system and database technology, the main contents of real-time database system include:

1. Real-time database model;
2. Real-time transaction scheduling: including concurrency control, conflict resolution, deadlock and other content;
3. Fault tolerance and error recovery;
4. Memory organization and management;
5. Access Admission Control;
6. I/O and disk scheduling;
7. Main memory database system;
8. The problem of inaccurate calculation;
9. The serializable problem of relaxation;
10. real-time SQL;
11. Predictability of real-time transactions;

Research status and development
Currently in the domestic comparison of the current foreign real-time database products have Wonderware company Industrial Sql,osisoft company PI, AspenTech company IP21 (Infoplus. 21). For example, 5,000-point database and 20-client application, several database prices are:

1. PI----$ 100,000, $6000 per interface, OPC interface charges;
2. infoplus.21----$ 110,000, 10,000 USD per interface, OPC interface no charge;
3. Industrial SQL Server----$ 65,000, each IDAS1200 USD, OPC link free.

Real-time Data database products
Pi stores all the data in a proprietary database, and for the stored mode of process data, only 6 domains per point can be defined by a user. Pi is a pure real-time database, if you want to implement more advanced enterprise application also need to be equipped with relational database.

Pi using the rotary door compression patented technology and unique two times filter technology, so that the data into the PI database has been the most effective compression, greatly saving the hard disk space. According to the calculation, 10,000 points per second of data storage for one year, only 4G of space, that is, a normal hard disk can also store 5-10 years of data. Is the most efficient, the simplest and most widely used real-time database, because of its outstanding performance, PI has increased its price several times, and PI in its documentation exposes its various algorithms, such as the above mentioned rotary door compression and two times filter.

The OSI company did not provide the PI server software and the client software in the Chinese version, but it is said that in the development, you can see a Chinese version of Datalink. Some of the domestic companies are also doing the authorization of the Chinese work for customers.

System performance
Each PI server can hold 1.5 million points (high-end servers) and can process 1.5 million points of data per second in the high-end product server of pi. On the client software Processbook, 1000 points can be taken from 2-year or 3-year history in a second time period.

Refer to the data provided by the OSI Company: The data value of the real-time information point is 1 days with an average change of 500, each information point occupies 3 bytes of storage space, that 10,000 points of storage for 1 years online is:

Number of changes × single point of storage x information points x1 years = Total space requirements
500x3x10000x365 = 5.475GB

Of course, hard drives are cheap, but saving space is not our starting point, the key is to quickly replay the data.

Device Interface Support
OSI provides more than 600 DCs interface software in the world, and can support OPC data acquisition, making PI database a bridge between enterprise production control system and management information system.

Client Tools
Pi-processbook: Organizes and displays process information, provides flowcharts, real-time and historical trends, and includes a VBA programming environment.
Pi-datalink:excel the embedded macro. Provides a very flexible process data analysis tool for end users. You can provide the necessary mathematical analysis using VBA, which provides the most general analysis tools, including: average, moving average, geometric average, standard deviation, cumulative value, and so on.
Pi-batch: Production batch process.
PI-ML: Manual input terminal (available in either software or hardware form).
Pi-ace: Allows the user to write equations. These equations can be reused without effort when capturing similar datasets.
PI ICE: The most innovative Web application for enterprise-class real-time performance management.
Pi ActiveView: Provides an existing PI Processbook display seamlessly to the Web.
Pi Alarm View: Summarize PI alarm Server information to display those data to any onsite customer or off-site customer in a hierarchical tree structure.
Pi Batch view: Displays PI batch data on a Windows desktop computer.
PI System Management tool: A set of applications that manage the PI system through the customer's PC.
PI Module Database: Divides the contents of the PI system into useful groups, helps organize real-time data, stores parameters or specifications, and makes them available for use in programs and displays at any time.
Rlink: Production data (PI) with SAP R/3, JD Edwards OneWorld, MRO software Maximo and Indus International passport/ A two-way gateway between ERP or EAM (Enterprise asset Management) systems such as EMPAC.

Two-time development tools
PI provides api,sdk, pi ODBC & PI OLE DB Two development tools for reading data from a database or writing data to a real-time database. In addition, the PI client procebook embedded in the VBA, convenient for the expansion of Procebook functions and customized.

PI API (Application programming Interface, Application development Interface)
Pi-api is a set of C-language functions that provide a common programming interface for accessing the PI system, and the application can access or manipulate the PI system by invoking the PI-API function. Many pi client software, including Pi Processbook, pi

DataLink, pi Profileview, etc., are through the Pi-api and PI server communication. The user can be called on the Unix,windows platform.

PI SDK (software Development Kit, software Development Kit)
The Pi SDK is another set of programming tools provided by PI to access the PI server and related subsystems. It uses Microsoft ActiveX technology, which includes an ActiveX in-process component, an ActiveX control, and other support code libraries such as online documentation, sample code, supporting documentation, and more. ActiveX is based on COM component technology and has developed language-agnostic features under the Microsoft Windows platform. Users can be in the development of simple. NET uses the Pi SDK to access the PI server,

It can also be used in efficient C + + and the Pi SDK is used in all other development tools that support COM technology.

Pi ODBC & PI OLE DB
ODBC is an open industry standard in the field of databases. OLE DB is a Microsoft COM-based database access interface standard. Using PI ODBC and PI OLE DB, users can access the PI system as if they were accessing a relational database. Pi ODBC or PI OLE DB based data interface programs and client applications that use standard SQL statements to access the PI database, including pi Archive, Pi Point database, or other configuration data.

Domestic users
OSI locates its database in the Enterprise Informatization integration platform, focusing on the development and service of real-time data software, mainly used in large-scale process industry users, such as power, petroleum, chemical and metallurgy. At present, China uses PI software enterprises to reach more than 100, mainly concentrated in power, petroleum, chemical industry, the domestic metallurgical industry users have Tangshan Iron and steel Company factory, Taiyuan Iron and Steel Group 2nd steel Plant, Shijiazhuang iron and Steel Company.

[Source: http://www.cnblogs.com/zljini/archive/2006/05/17/402422.html]

Introduction and comparison of real-time databases