oracle streams - how to get last successfully applied scn for crashed apply?
Found it.


  Low-Watermark and High-Watermark for an Apply Process
  
  The low-watermark for an apply process is the system change number
  (SCN) up to which all LCRs have been applied. That is, LCRs that were
  committed at an SCN less than or equal to the low-watermark number
  have definitely been applied, but some LCRs that were committed with a
  higher SCN also might have been applied. The low-watermark SCN for an
  apply process is equivalent to the applied SCN for a capture process.
  
  The high-watermark for an apply process is the SCN beyond which no
  LCRs have been applied. That is, no LCRs that were committed with an
  SCN greater than the high-watermark have been applied.
  
  You can view the low-watermark and high-watermark for one or more
  apply processes by querying the V$STREAMS_APPLY_COORDINATOR and
  ALL_APPLY_ PROGRESS data dictionary views.