Upgrade from 10.2.0.2 to 10.2.0.4 in Physical DataGuard Environment.

Note 278641.1 in the upgrade readme.txt recommends starting with 

1.  apply binaries to primary and secondary

2.  run catupgrd.sql on primary

3.  then (reading between the lines) alllow the sql from the catupgrad.sql to flow to the secondary.

4.  Issue

    a)  I need to minimize downtime on the primary

         1.  running catupgrd.sql can take 10mins on the primary (highly undesirable) 

5.  Feasible scenarios seem to include

   a)  using a transient logical standby - looks messy - and doing a switchover

6.  My thought is to simply

    a)  stop shipping logs to standby

    b) Upgrade standby

    c)  Switch to standby - takes about 1 min

    d) Upgrade former primary