As part of making truncate atomic, checkpoint was added before
  truncate was mark done. This checkpoint helped in making current
  state consistent in-turn helped in skipping application of redo-entries
  from action before truncate (note these redo entries may have reference
  to a page that may not exist post truncate).

  Checkpoint takes significant time if parallel RW-workload is active
  eventually delaying truncate.

  In new approach, a special redo log record is written at start of truncate
  to cache space_id and current-lsn. In case of crash, post truncate
  before system enforced checkpoint this redo log record helps in blocking
  application of redo-entry from action before truncate but allows application
  of redo-entry from action post truncate.

  Reviewed by: Jimmy Yang (jimmy.yang@oracle.com)
  RB: 9305