每个数据库的一个主数据文件属于主文件组。
A of every database advocate data file belongs to main body of a court verdict group.
采用多个数据文件时，主数据文件用于存储系统对象和表，次要数据文件用于存储用户数据和索引。
When using many data document, advocate data file is used at storage system object and watch, secondary data file is used at memory user data and index.
对于1gb左右规模的数据库，一个数据文件就够了，如果有次要数据文件，主数据文件中有管理次要数据文件的指针。
Control the database of dimensions to 1gb, file of a data is enough, if have secondary data file, advocate the index that there is file of administrative secondary data in data file.
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