What are these background processes?

Here is a listing of background processes from one of my Oracle 7.3 instances...

  oracle 26497     1  1 15:56:43 ?         0:01 ora_d001_test
  oracle 26491     1  0 15:56:43 ?         0:00 ora_reco_test
  oracle 26487     1  3 15:56:43 ?         0:16 ora_lgwr_test
  oracle 26489     1  0 15:56:43 ?         0:11 ora_smon_test
  oracle 26483     1  5 15:56:43 ?         0:28 ora_dbwr_test
  oracle 26485     1  0 15:56:43 ?         0:00 ora_arch_test
  oracle 26493     1  2 15:56:43 ?         0:03 ora_s000_test
  oracle 26481     1  6 15:56:43 ?         0:18 ora_pmon_test
  oracle 26495     1  0 15:56:43 ?         0:00 ora_d000_tes

What are the d0000, d0001, and s000 processes? Received on Wed Oct 15 1997 - 00:00:00 CDT