Syntax options:

    ASYNC PREFETCH IS ENABLED | ASYNC PREFETCH IS DISABLED

    Specifies whether or not Oracle Rdb reduces the amount of time
    that a process waits for pages to be read from disk by fetching
    pages before a process actually requests the pages.

    Prefetch can significantly improve performance, but it may
    cause excessive resource usage if it is used inappropriately.
    Asynchronous prefetch is enabled by default. For more information
    about asynchronous prefetch, see the Oracle Rdb7 Guide to
    Database Performance and Tuning.

    You can enable asynchronous prefetch by defining the logical name
    RDM$BIND_APF_ENABLED.