Changing System-Level Options

The following suggestions about system-level options may help improve performance of an import operation:

  • Create and use one large rollback segment and take all other rollback segments offline. Generally a rollback segment that is one half the size of the largest table being imported should be big enough. It can also help if the rollback segment is created with the minimum number of two extents, of equal size.


    Oracle recommends that you use automatic undo management instead of rollback segments.

  • Put the database in NOARCHIVELOG mode until the import is complete. This will reduce the overhead of creating and managing archive logs.

  • Create several large redo files and take any small redo log files offline. This will result in fewer log switches being made.

  • If possible, have the rollback segment, table data, and redo log files all on separate disks. This will reduce I/O contention and increase throughput.

  • If possible, do not run any other jobs at the same time that may compete with the import operation for system resources.

  • Ensure that there are no statistics on dictionary tables.

  • Set TRACE_LEVEL_CLIENT=OFF in the sqlnet.ora file.

  • If possible, increase the value of DB_BLOCK_SIZE when you re-create the database. The larger the block size, the smaller the number of I/O cycles needed. This change is permanent, so be sure to carefully consider all effects it will have before making it.