You can copy games into an openings book to extend it. You can drag & drop another database symbol onto the book symbol, or drag & drop a selection of games list or opening keys onto it.
Games
You can set the number of games you want to copy.
Length
Crucial for the size of the resulting tree is the length of the variations which are put into the tree. It is not very meaningful to put entire games into it, so you should truncate them at a specific point.
ChessBase allows you to limit the length of the variations in two different ways.
| 1. | You can specify that the absolute length of every variation should be exactly “n” moves. |
| 2. | It is usually much more sensible to limit the length of the variations relative to the ECO classification. This results in long variations for theoretical main lines (ECO classification position found late in the game) and short variations for side lines i.e. early deviations. |
Obviously, if you choose a shorter length the tree will be compact. But then you are liable to lose some valuable information. If you choose a very large value then the tree will be gigantic, and it will contain a lot of superfluous information. A good practical value for adding games to the tree is the default of ECO + 20.
Variations
You can also include variations, i.e. analysis that might be included in the games. But these are not included in the statistical analysis.