A method for processing data to efficiently generate system information characterizing the data stored in a data storage system, the method including: reading data from an interface to the data storage system, and storing two or more sets of summary data (200A-200F) summarizing data stored in different respective data sources in the data storage system; and processing the stored sets of summary data (200A-200F), using at least one processor, to generate system information characterizing data from multiple data sources in the data storage system, wherein a stored set of summary data (200A-200F) summarizing data stored in a particular data source includes, for at least one selected field of records in the particular data source, a corresponding list of value entries, with each value entry including a value appearing in the selected field and wherein each value entry in the list of value entries corresponding to the particular data source further includes location information identifying respective locations within the particular data source of records in which the value appears in the selected field, the processing including: analyzing the stored sets of summary data (200A-200F) to select two or more data sources that store data satisfying predetermined criteria, and generating the system information including information identifying a potential relationship between fields of records included in different data sources based at least in part on comparison between distinct values from a stored set of summary data (200A-200F) summarizing a first of the selected data sources and distinct values from a stored set of summary data (200A-200F) summarizing a second of the selected data sources. reading data from an interface to the data storage system, and storing two or more sets of summary data (200A-200F) summarizing data stored in different respective data sources in the data storage system; and processing the stored sets of summary data (200A-200F), using at least one processor, to generate system information characterizing data from multiple data sources in the data storage system, wherein a stored set of summary data (200A-200F) summarizing data stored in a particular data source includes, for at least one selected field of records in the particular data source, a corresponding list of value entries, with each value entry including a value appearing in the selected field and wherein each value entry in the list of value entries corresponding to the particular data source further includes location information identifying respective locations within the particular data source of records in which the value appears in the selected field, the processing including: analyzing the stored sets of summary data (200A-200F) to select two or more data sources that store data satisfying predetermined criteria, and generating the system information including information identifying a potential relationship between fields of records included in different data sources based at least in part on comparison between distinct values from a stored set of summary data (200A-200F) summarizing a first of the selected data sources and distinct values from a stored set of summary data (200A-200F) summarizing a second of the selected data sources. analyzing the stored sets of summary data (200A-200F) to select two or more data sources that store data satisfying predetermined criteria, and generating the system information including information identifying a potential relationship between fields of records included in different data sources based at least in part on comparison between distinct values from a stored set of summary data (200A-200F) summarizing a first of the selected data sources and distinct values from a stored set of summary data (200A-200F) summarizing a second of the selected data sources.