Difference in gathering statistics

The major difference between DBMS_STATS.GATHER_DATABASE_STATS_JOB_PROC and DBMS_STATS.GATHER_DATABASE_STATS is that GATHER_DATABASE_STATS_JOB_PROC is smart enough to start the analyze with most in need objects.

Wait event : Read by other session

In case the contention is on indexes, I would recreate the primary key using reverse index.
Before do this , you should be aware the drawback regarding range scan.

This was my answer at
http://forums.oracle.com/forums/post!reply.jspa?messageID=9432150