Configuring the Engine

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As already discussed in the Architecture topic, the TEDBEngine component represents the engine in ElevateDB. The following information will show how to configure the engine for use as a client engine in an application or as an server engine. The TEDBEngine EngineType property controls whether the engine is behaving as a local engine or a server engine.


Character Set

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The TEDBEngine CharacterSet property specifies which character set, ANSI or Unicode, to use for reading and writing the configuration file and all databases and tables. This property defaults to a value that matches the default string type used by the current compiler. For example, with Delphi XE the default string type is a Unicode string, so this property will default to csUnicode when used with Delphi XE. This setting can be overridden on a per-session basis by modifying the TEDBSession CharacterSet property.

Configuration Path

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The TEDBEngine ConfigMemory and ConfigPath properties specify where the engine should look for the configuration file to use for the application, if running as a client engine, or the server, if running as a server engine. The configuration file is used to store the information in the Configuration database in ElevateDB. If the ConfigMemory property is set to True, then the configuration file will be "virtual" and stored in the process memory. If the ConfigMemory property is False and the path specified for the ConfigPath property does not exist, then an error will be raised when the engine is started (Active=True). If the path exists, but the configuration file does not exist in the path, then the ElevateDB engine will create the configuration file as necessary.


Temporary Tables Path

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The TEDBEngine TempTablesPath property controls where ElevateDB creates any temporary tables that are required for storing query result sets. By default, the TempTablesPath property is set to the user-specific temporary tables path for the operating system.

Engine Signature

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The TEDBEngine Signature property controls the engine signature for the engine. The default engine signature is "edb_signature". The engine signature in ElevateDB is used to "stamp" all configuration files, catalog files, table files, backup files, update files, and streams created by the engine so that only an engine with the same signature can open them or access them afterwards. If an engine does attempt to access an existing table, backup file, update file, or stream with a different signature than that of the table, backup file, update file, or stream, an EEDBError exception will be raised. The error that is raised when the access fails due to an invalid engine signature is 100 (EDB_ERROR_VALIDATE).

Also, if the EngineType property is set to etClient, the engine signature is used to stamp all requests sent from a remote session to an ElevateDB Server. If the ElevateDB Server is not using the same engine signature, then the requests will be treated as invalid and rejected by the ElevateDB Server. If the EngineType property is set to etServer, the engine signature is used to stamp all responses sent from the ElevateDB Server to any remote session. If the remote session is not using the same engine signature then the requests will be treated as invalid and rejected by the ElevateDB Server. In summary, both the remote sessions and the ElevateDB Server must be using the same engine signature or else communications between the two will be impossible.


Encryption Password

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You can use the EncryptionPassword property to modify the encryption password used by ElevateDB for all file encryption purposes. ElevateDB uses this password for all configuration, database catalog (for encrypted catalogs), and table files (for encrypted tables) encryption. The default encryption password is 'elevatesoft'.

ElevateDB uses the Blowfish block cipher encryption algorithm with 128-bit MD5 hash keys for encryption. Please see the Encryption topic for more information.

Licensed Sessions

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You can specify that a certain maximum number of concurrent licensed sessions be allowed by modifying the TEDBEngine LicensedSessions property. The default value for this property is 4096 sessions. Setting this property to a lower figure will allow no more than the specified number of sessions to concurrently access the same configuration.

Buffered File I/O

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You can specify whether to enable buffered file I/O in ElevateDB by modifying the TEDBEngine BufferedFileIO property. The default value for this property is False. If you enable buffered file I/O, you can use the BufferedFileIOSettings and BufferedFileIOFlushInterval properties to control how the buffered file I/O behaves.

The following is an example of how the buffered file I/O could be configured:

Engine.BufferedFileIO:=True;
with Engine.BufferedFileIOSettings do
   begin
   { Lock files don't use buffering }
   Add('"*EDBConfig.EDBLck",1,1,0,False');
   Add('"*EDBDatabase.EDBLck",1,1,0,False');
   { Configuration and catalog files:
     64KB block size
     4MB buffer size
     0-second flush age (always write any dirty buffers during flush checks)
     Always force flush to disk call in OS }
   Add('"*EDBDatabase.EDBCfg",64,4,0,True');
   Add('"*EDBDatabase.EDBCat",64,4,0,True');
   { Smaller database table files:
     64KB block size
     32MB buffer size
     120-second flush age
     Don't force flush to disk call in OS }
   Add('"*Customer.EDBTbl",64,32,120,False');
   Add('"*Customer.EDBIdx",64,32,120,False');
   Add('"*Customer.EDBBlb",64,32,120,False');
   { Larger database table files:
     64KB block size
     128MB-256MB buffer sizes
     120-second flush age
     Don't force flush to disk call in OS }
   Add('"*Orders.EDBTbl",64,128,120,False');
   Add('"*Orders.EDBIdx",64,256,120,False');
   Add('"*Orders.EDBBlb",64,256,120,False');
   end;

Please see the Buffering and Caching topic in the SQL manual for more information on buffered file I/O in ElevateDB.

File Names and Extensions

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The following file customziations can be made for the engine:


Server Configuration

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There are no extra steps required in order to use the TEDBEngine component in ElevateDB as a client engine since the default value of the EngineType property is etClient. However, in order to use the TEDBEngine component in ElevateDB as an ElevateDB Server you will need to make some property changes before starting the engine.

The TEDBEngine component has several key properties that are used to configure the ElevateDB Server, which are described below in order of importance:


ElevateDB comes with a default GUI ElevateDB Server project for Delphi called edbsrvr.dpr (Windows only). You can examine the source code of these projects to see how you would go about setting up a TEDBEngine component as an ElevateDB Server in a project. Both of these projects are also provided in compiled form with ElevateDB. You can find these servers in the \servers\edbsrvr subdirectories under the main ElevateDB installation directory, and you can find the source code to these servers in the \source subdirectory under each server's directory.

Starting the Engine

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Once you have configured the engine using the above information, starting the engine is quite simple. All you need to do is set the Active property to True. The following shows an example of how one might configure and start an ElevateDB Server using the default global Engine function in the edbcomps unit (Delphi and Lazarus) or edbcomps header file (C++):

with Engine do
   begin
   ConfigPath:='\MyApplication';
   ServerName:='MyTestServer';
   ServerDescription:='My Test Server';
   { Only listen on this IP address }
   ServerAddress:='192.168.0.1';
   Active:=True;
   end;