Seamless TAB

Seamless files are a collection of contiguous files that are treated as one. Spectrum Spatial supports seamless tables for native TAB, native extended TAB (NativeX), and raster/grid files.

Spectrum Spatial treats seamless tables as a read-only data source.

File Handle Pool for Seamless Tables

If your native TAB files do not change frequently, set the volatility to false and take advantage of a file handle pool that minimizes the file opening and closing during operations. This is only available to non-volatile native and seamless TAB files and shapefiles.

The file handle pool is enabled by default. Configuration of the file handle pool is done through the tab-file-handle-pool.properties file, located in the \server\modules\spatial folder.

For seamless tables, there is general formula for maximizing the performance of the file handle pool. Specifically, you have to calculate the maximum number of handles that can be allocated to the pool (maxTotal). Use the following steps to calculate the maxTotal:

  1. Find the seamless table with the most number of sub-tables, and note the number of sub-tables (#ofsub-tables).
  2. Determine the number of threads you are using (#ofthreads).
  3. The formula is (3 + (3 x #ofsub-tables)) x #ofthreads = maxTotal. If your seamless tables do not have .ind files, the formula is (2 + (2 x #ofsub-tables)) x #ofthreads = maxTotal.

For example, if you are using the entire seamless USA table, there are .ind files, there are 54 sub-tables, and you are using 8 threads. The calculation for maxTotal is (3 + (3 x 54)) x 8 = 1320.

For more information on how seamless tables interact with Spectrum Spatial and about the file handle pool, see MapInfo Native TAB and Raster/Grid TAB.