Technical architecture and ways of operating SIS
Article 4
1. SIS shall be composed of: (a) a central system (Central SIS) composed of: (i) a technical support function (‘CS-SIS’) containing a database (the ‘SIS database’), and including a backup CS-SIS; (ii) a uniform national interface (‘NI-SIS’); (b) a national system (N.SIS) in each of the Member States, consisting of the national data systems which communicate with Central SIS, including at least one national or shared backup N.SIS; and (c) a communication infrastructure between CS-SIS, backup CS-SIS and NI-SIS (‘the Communication Infrastructure’) that provides an encrypted virtual network dedicated to SIS data and the exchange of data between SIRENE Bureaux, as referred to in Article 7(2). An N.SIS as referred to in point (b) may contain a data file (a ‘national copy’) containing a complete or partial copy of the SIS database. Two or more Member States may establish in one of their N.SIS a shared copy which may be used jointly by those Member States. Such shared copy shall be considered as the national copy of each of those Member States. A shared backup N.SIS as referred to in point (b) may be used jointly by two or more Member States. In such cases, the shared backup N.SIS shall be considered as the backup N.SIS of each of those Member States. The N.SIS and its backup may be used simultaneously to ensure uninterrupted availability to end-users. Member States intending to establish a shared copy or shared backup N.SIS to be used jointly shall agree their respective responsibilities in writing. They shall notify their arrangement to the Commission. The Communication Infrastructure shall support and contribute to ensuring the uninterrupted availability of SIS. It shall include redundant and separated paths for the connections between CS-SIS and the backup CS-SIS and shall also include redundant and separated paths for the connections between each SIS national network access point and CS-SIS and backup CS-SIS. 2. Member States shall enter, update, delete and search SIS data through their own N.SIS. The Member States using a partial or a complete national copy or a partial or complete shared copy shall make that copy available for the purpose of carrying out automated searches in the territory of each of those Member States. The partial national or shared copy shall contain at least the data listed in points (a) to (v) of Article 20 (3). It shall not be possible to search the data files of other Member States' N.SIS except in the case of shared copies. 3. CS-SIS shall perform technical supervision and administration functions and have a backup CS-SIS, capable of ensuring all functionalities of the principal CS-SIS in the event of failure of that system. CS-SIS and the backup CS-SIS shall be located in the two technical sites of eu-LISA. 4. eu-LISA shall implement technical solutions to reinforce the uninterrupted availability of SIS either through the simultaneous operation of CS-SIS and the backup CS-SIS, provided that the backup CS-SIS remains capable of ensuring the operation of SIS in the event of a failure of CS-SIS, or through duplication of the system or its components. Notwithstanding the procedural requirements laid down in Article 10 of Regulation (EU) 2018/1726 eu-LISA shall no later than 28 December 2019, prepare a study on the options for technical solutions, containing an independent impact assessment and cost-benefit analysis. 5. Where necessary in exceptional circumstances, eu-LISA may temporarily develop an additional copy of the SIS database. 6. CS-SIS shall provide the services necessary for the entry and processing of SIS data, including searches in the SIS database. For the Member States which use a national or shared copy, CS-SIS shall: (a) provide online updates for the national copies; (b) ensure synchronisation of and consistency between the national copies and the SIS database; and (c) provide the operation for initialisation and restoration of the national copies. 7. CS-SIS shall provide uninterrupted availability.