[Oracle] common tool set-SQL * Loader

[Oracle] common tool set-SQL * Loader principle SQL * Loader is a tool provided by Oracle for data loading, it is suitable for business analysis databases (data warehouses) and can process flat files in multiple formats. batch data loading is more efficient than traditional data insertion. It is as follows: Control File: The file used to control the behavior of Data Import (the most important file ). Parameter file (optional) data file: flat file for storing source data error file: During data loading, put data that cannot be correctly loaded into the wrong file (such as data format problems, data type problems, etc.) discard the file (optional): some data, although the data format, data type is no problem, but it is filtered out by the logical conditions (set in the control file) and will be put into the log file of the lost file: record the data loading process of SQL * Loader and directly load the path in SQL * Loader. To improve performance, Direct path loading is generally used (set Direct = TRUE ). Oracle provides two types of insert statements: Regular insert (conventional insert) and direct insert (direct-path insert). direct insert at the cost of some functions, in exchange for efficient loading of a large amount of data. Direct path loading inserts data directly to the high-water level (HWM) of the segment to be modified, and generates a minimum number of undo (only the undo of the data dictionary is generated, it does not generate undo of data in blocks and does not pass the high-speed cache (SGA). Therefore, it has better performance than regular inserts. Restrictions on direct path loading: 1) a table can only have one direct path at the same time. Therefore, it is not suitable for insertion of small data volumes and is only suitable for loading large volumes of data. 2) idle space in HWM is not used; 3) A table cannot be operated on by the same session while inserting a direct path (select is not supported); 4) only insert inot... select... statements, merge statements, and applications that use the OCI direct path interface can be used.