SQL*Loader uses the SQL array-interface option to transfer data to the database. Multiple rows are read at one time and stored in the bind array. When SQL*Loader sends the Oracle database an INSERT command, the entire array is inserted at one time. After the rows in the bind array are inserted, a COMMIT statement is issued.
The determination of bind array size pertains to SQL*Loader's conventional path option. In general, it does not apply to the direct path load method because a direct path load uses the direct path API. However, the bind array might be used for special cases of direct path load where data conversion is necessary.
Oracle Call Interface Programmer's Guide for more information about the concepts of direct path loading