IBM DB2 manual Importing data, Import utility, Different import modes

For a detailed description of the export utility, refer to the DB2 Infocenter:

http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp?topic=/com.ibm.d

b2.luw.admin.dm.doc/doc/c0004587.html

Importing data

You can use either the import utility or the load utility to move the exported data into the target database. The import utility is based upon the SQL statements and all the integrities and constraints are obtained during import. In general, the import utility is used if the amount of data is not to big. For large amount of data, the load utility is much faster. However, the load utility does not set referential integrity, which mean that foreign key relations are not checked. After the load utility has completed, some tables might be in integrity pending state and are not accessible. You can use the set integrity command to validate dependencies and bring tables back into accessible mode.

Another difference between import and load is that the import utility cannot override the columns defined as generated always. The load utility is required if

there are such columns in the tables.

Assuming that there are no special requirements or data restrictions that force us to choose one over the other, the choice can usually be based on the amount of data and the performance requirements. If the data volume is large and the performance is a concern, the load utility is preferable.

For a thorough comparison of these two methods, refer to the DB2 Infocenter:

http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/topic/com.ibm.db2.luw.admi

n.dm.doc/doc/r0004639.html

Import utility

The import utility populates a table with data by using the SQL INSERT statement. There are several options on how to control the behavior of the utility. The most important option is the import mode. This mode controls what to do with existing data in the tables. Table 5-2lists the different modes.

Table 5-2 The different import modes

Mode	Description
INSERT	Insert the data into the target table without changing existing data.
INSER_UPDATE	Update rows with matching primary key values with values of the
	input rows. If there is no matching row, insert the data row into the
	table.
REPLACE	Delete all the existing data and insert the input data. The table and
	index definitions are kept.

236DB2 Deployment Guide