For both the conventional path and the direct path, SQL*Loader maintains all existing indexes for a table.
To avoid index maintenance, use one of the following methods:
Drop the indexes before beginning of the load.
Mark selected indexes or index partitions as Index Unusable before beginning the load and use the SKIP_UNUSABLE_INDEXES parameter.
Use the SKIP_INDEX_MAINTENANCE parameter (direct path only, use with caution).
By avoiding index maintenance, you minimize the amount of space required during a direct path load, in the following ways:
You can build indexes one at a time, reducing the amount of sort (temporary) segment space that would otherwise be needed for each index.
Only one index segment exists when an index is built, instead of the three segments that temporarily exist when the new keys are merged into the old index to make the new index.
Avoiding index maintenance is quite reasonable when the number of rows to be loaded is large compared to the size of the table. But if relatively few rows are added to a large table, then the time required to resort the indexes may be excessive. In such cases, it is usually better to use the conventional path load method, or to use the SINGLEROW parameter of SQL*Loader. For more information, see "SINGLEROW Option".