How much disk overhead will the indexing require?
The overhead – the amount of space needed for the DR$ index tables – varies between about 25% of the original text volume, and 100%. Generally, the larger the total amount of text, the smaller the overhead, but many small records will use more overhead than fewer large records. Also, “clean” data (such as published text) will require less overhead than “dirty” data such as emails or discussion notes, since the “dirty” data is likely to include many unique words from mis-spellings, abbreviations, etc. Theme indexes are generally much smaller than text indexes. Creating ONLY a theme index will generally require very little storage, but creating only a text index will not save you much space over a combined index (though it is likely to be significantly faster).
