In publications section of application, I'm asked what database the journal is indexed in. Where can I find that information? I am applying to a university for a PhD and in the application it asks for information on journal publications. And under that it asks for journal's Impact factor and database the journal is indexed in.  

What is meant by database the journal is indexed in? How can I find it?      

I have my journal submitted to BMC systems biology and I found the 2015 impact factor to be 2.213. What is the database the journal is indexed in?
It sounds like a poorly worded question.

However, if I were to guess their intentions, they might be interested in whether the journal appears in the "Science Citation Index - Expanded" or "Social Sciences Citation Index". Or another influential one is whether it is in the Proquest index.

The reason I say this, is that inclusion in these indices are sometimes used as a minimal criteria for legitimacy as a journal for inclusion in world rankings.

E.g., The Shanghai rankings use:


  ARWU uses six objective indicators to rank world universities,
  including the number of alumni and staff winning Nobel Prizes and
  Fields Medals, number of highly cited researchers selected by Thomson
  Reuters, number of articles published in journals of Nature and
  Science, number of articles indexed in Science Citation Index -
  Expanded and Social Sciences Citation Index, and per capita
  performance of a university. More than 1200 universities are actually
  ranked by ARWU every year and the best 500 are published.


You can search for inclusion in Science and Social Science Citation Index here.