Server Engine
Wed, 03/04/2009 - 20:02 | 
hdanzl
The Server Engine Settings define how the core server engine operates.
Server Name
As a unique identifier, the server needs a name, which is entered in the Server Name option.
Max RAM
Max RAM defines the maximum amount of physical memory the server engine is allowed to allocate for its operation. This setting is in Megabytes and should be set. Best performance is achieved if it is set to a value large enough so that all tables fit into this memory. If this value is set to -1, the server will use a maximum of 50% of the physical memory available to the machine. This setting is very important for optimal performance of NexusDB and should be adjusted from time to time as the database size grows above its initial setting.
Temporary Storage
The settings for Temporary Storage are Path and Size. NexusDB uses its own temporary storage management and files instead of using the normal windows page file. This increases its performance and allows for dedicated virtual memory allocation for the database server. The files that NexusDB creates are stored in the directory identified by the path setting and have the maximum size stated in the size setting. The files are created as maximum size when the server engine is started with a special file system flag which makes sure they are deleted as soon as the process ends, even if it is killed (e.g. via the task manager or Delphi).
Engine Options
The Engine Options enable the user to change certain behaviour of the database server.
| • | The read only setting sets all databases and thus tables of the server to read only. This means also that the SQL data manipulation commands (insert, update, etc.) are not enabled anymore. It is still possible though to create in-memory tables. |
| • | This leads us directly to the InMem only option, which is restricting the database server to in-memory tables only. No tables are saved to disk if this option is enabled and thus if the server is closed all data is lost. |
| • | Close Inactive Tables and Close Inactive Folders influence the file caching of the server. Every open database and table in NexusDB has an exclusive file lock. This ensures that no other server or application can access the files while they are opened by the NexusDB server. In default configuration, these two options are disabled and the server keeps the locks once they are established and thus can safely keep them in cache if there is enough room. If a client reopens the tables/databases again, the server engine can access them from the much faster memory instead of having to access them on disk again. |
| • | Force Failsafe makes the server work in failsafe mode only. Please note that this slows down the server significantly, but in certain circumstances and environment, data safety and consistency is essential. If the option is enabled the server engine writes a journal for every transaction and only if the transaction is successfully completed and the journal committed the actual transaction is considered successful. Otherwise the engine automatically applies the action set in the Failsafe mode setting. |
| • | Finally the Secure Server option forces users to logon when establishing a connection and an admin user to log on to the server user interface. Please look at the following paragraph for more information on Users. |
Failsafe Mode
If Force Failsafe is enabled, this option defines which action the server takes on restart, if he finds that a previous transaction was not successful.
The default option is Always Rollback, which always undoes unsuccessful transactions. Always Commit is the opposite while Dialog pops up a dialog and lets the user decide what to do.
Please note that Dialog should never be used if the server is running as a service or in unattended mode, as the server will not start until a Failsafe mode was selected in this dialog.
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