The restricted acts here are extraction and re-utilisation. In relation to the contents of a database, extraction means the permanent or temporary transfer of those contents to another medium by any means or in any form, and re-utilisation means making those contents available to the public by any means. In Apis-Hristovich EOOD v Lakorda AD (C545/07)  3 C.M.L.R. 3 ,  E.C.D.R. 13) the ECJ made clear that the difference between permanent and temporary transfer is based on the length of time during which the extracted materials are stored in a medium other than the original database.
The ECJ emphasised that the rights to prevent extraction and re-utilisation must be construed in the context of the wider objectives of the sui generis right, namely the protection of the investment of the maker of the database. Consequently it concluded that the fact that the act of extraction or re-utilisation is for the purpose of creating another database (whether in competition with the original database or not, of a different size, or part of wider activities) is irrelevant. Also, in The British Horseracing Board Ltd v William Hill Organisation Ltd (C203/02)  R.P.C. 13 it was irrelevant whether the act in question was done for a commercial or non-commercial purpose.
If a database right subsists in an electronic database, then downloading a substantial part of that database without authorisation from the owner of database right will amount to an infringement. Furthermore, even if a single item or value is not in itself of sufficient qualitative importance, such that its isolated downloading will not amount to infringement, its repeated and systematic downloading may be an infringement. Substantial, in relation to any extraction or re-utilisation, means substantial in terms of quantity or quality or a combination of both.