Thank you Christian,
I may try it later as a last option. I hope you can find an alternative solution.
Is there also an option to define inside the part only the xpaths which I would need?
Otherwise, many elements and attributes which I don't need are being indexed.

Another question, how can I know if the following values have been exceeded in a specific database? Quoting:

MAXLEN

Signature MAXLEN [int]
Default 96
Summary Specifies the maximum length of strings that are to be indexed by the name, path, value, and full-text index structures. The value of this option will be assigned once to a new database, and cannot be changed after that.

MAXCATS

Signature MAXCATS [int]
Default 100
Summary Specifies the maximum number of distinct values (categories) that will be stored together with the element/attribute names or unique paths in the Name Index or Path Index. The value of this option will be assigned once to a new database, and cannot be changed after that. 

With kind regards,
Menashè
On 06/23/2015 12:51 PM, Christian Grün wrote:
Is there an option to ask BaseX to parse only a part of the imported xml
files under a specific xpath, (or at least limit useless indexing of non
relevant components)? I don't need the rest of the xml files, even though
it's not too big. Maybe it can help.

The usual approach is to simply create another database that only
contains the relevant parts of your document. This can directly be
done in XQuery (using db:create, db:add, ...), or, if memory
consumption is too high, by exporting and importing parts of your
document.

Hope this helps,
Christian