Although importing large volumes of data can be time consuming, there are a few things you can do to save time:
Place data files on a separate physical disk drive from the database. This could avoid excessive disk head movement during the load.
Extend the size of the database, as described in ALTER DBSPACE statement. This command allows a database to be extended in large amounts before the space is required, rather than in smaller amounts when the space is needed. As well as improving performance for loading large amounts of data, it also serves to keep the database more contiguous within the file system.
Use temporary tables to load data. Local or global temporary tables are useful when you need to load a set of data repeatedly, or when you need to merge tables with different structures.
If you are using the LOAD TABLE statement, do not start the database server with the -b option (bulk operations mode); it is not necessary.
If you are using the INPUT or OUTPUT statement, run Interactive SQL or the client application on the same computer as the database server. Loading data over the network adds extra communication overhead. You may want to load new data at a time when the database server is not busy.