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- Overview
- How to?
- Principle
- When should the network frames be compressed?
- How to use the compression of frames?
Pattern compression (ADSL, 3G, Edge, VPN, etc.)
 Disponible solo con este tipo de conexión
A frame is a packet of data that flows through the network. HFSQL Client/Server, like all the DBMSs, uses the frames to establish the communication between the Server and the Client computer. The response speed of a server depends on the circulation speed of the frames through the network and on the size of these frames. In local network, the speed is so high that the size of the frame is not very important. For a remote access (ADSL, 3G, VPN, ...), the size of the frame is more important. In this context, a reduction of the size of the frames increases performance. In a context of remote communication, the compression of the frames is very important especially if the connection speed is slow and if the invoicing depends on the volume of transmitted data. Principle The principle for compressing the frames is as follows: - The data to transmit is compressed on the server (or on the client).
- The compressed data is transmitted to the client (or to the server).
- The data is decompressed on the client (or on the server).
The benefit brought by the data compression depends on the configuration used. For example, if the client workstation is a powerful one using a slow connection, it's a good idea to use pattern compression: the compression/decompression time will be infinitesimal compared to the time saved for data transmission. When should the network frames be compressed? The choice must be based on 3 parameters: - the speed of the network used,
- the CPU performance of the client computers
- the type of the transmitted data.
The importance of each parameter depends on the two other ones so no standard formula is available. However, you will find some tips that help you make this choice: If you're using a network with a speed greater than 10 Mbits/second, you shouldn't compress the patterns. If the network used (GRPS, EDGE or 3G type) is invoiced according to the amount of transmitted data, we advise you to compress the frames in order to reduce costs. If you're transporting large quantities of binary memo data (images, video, zip sound, etc.), pattern compression won't be of interest. In all the other cases: - on client computers with high-performance processors and if your application uses text or text memo data, it may be useful to compress the frames.
- on client computers with less powerful processors, the lower the transfer speed, the more useful the compression.
You will need to compare different aspects using the Performance profiler. HConnectionQuality can be used as a last resort to compare the performance of compressed and decompressed connections. How to use the compression of frames? The compression of frames is a property of the connection. To use the compression of frames: - if the connection is defined in the data model editor, you have the ability to modify the characteristics of the connection:
- on the "Análisis" tab, in the "Conexión" group, click "Conexiones".
- Select the desired connection.
- display the "Advanced" tab and check "Compress the data".
- if the connection is defined programmatically, several methods are available:
- functions HOpenConnection and HDescribeConnection: parameter <Informations étendues> is used to specify whether compression is to be performed.
- property Compression (can be used, for example, with type Connection): this property defines whether data compression is to be performed.
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