Buffers=n

    Specifies the number of database buffers used for storing data
    during the load operation. If no value is specified, the default
    value for the database is used. (The default value for the
    database is defined by the logical name RDM$BIND_BUFFERS, or
    if the logical is not defined, can be determined by using the
    RMU Dump command with the Header qualifier. The RDM$BIND_BUFFERS
    logical name, if defined, overrides the value displayed with the
    RMU Dump command.) Fewer I/O operations are required if you can
    store as much data as possible in memory when many indexes or
    constraints are defined on the target table. Therefore, specify
    more buffers than allowed by the default value to increase the
    speed of the load operation.

    See the Oracle Rdb7 Guide to Database Performance and Tuning
    for detailed recommendations on setting the number of database
    buffers.