NexusDB V3 Manual

File Descriptors

NexusDB allows the developer to split the data of tables into different physical files. Each of these files is defined by a File Descriptor.

You will always find a File1 descriptor in this dialog, which is the main file. It can't be deleted and always uses the default file extension (the according field is empty), which can be set by the database developer in the TnxServerEngine properties.

File Extension

For every file except File1 (the main file) you can set your own file extension. Take care to not give any two files the same extension as this will lead to a "Can't open tablename" error when trying to create the table. Please note that in the shipped version the default file extension is NX1 and thus the example above would trigger exactly this error.

Block Size

Blocksize is restricted to values of 4, 8, 16, 32 and 64 kilobytes.  The server engine will ensure that each block can hold at least one record and conforms to index block page requirements as well.  As a heuristic you should bear in mind that larger block sizes take longer to read/write to disk.

Initial Blocks

Initial Blocks is the number of blocks the table is initially created with. The default for Initial Size is 4, which is the minimum number of blocks NexusDB needs to totally define a table.

Grow Blocks

Grow Blocks is the number of blocks it grows by on disk when more space is needed in the file. To reduce disk fragmentation you should use a large value for Grow Size, especially if you have a table with a large number of indices and/or is being continuously appended to. The default is nonetheless set to 1 to ensure minimum file size.