Can one see what patches are applied to Oracle?

With the Unix "what" command one can see what patches are applied to an executable. The Oracle implementation of what is owhat.

The 'what' command delves into a file and extracts SCCS version control information from that file, if any exists. For more details, look up 'man what'. Look at this example:

$ cd $ORACLE_HOME/bin
$ owhat oracle
Oracle patches in /app/oracle/product/7.3.4/bin/oracle:
        sf.c VLFS patch 08/1/96
        sksa.c VLFS patch 08/1/96
        sp.c VLFS patch 08/1/96
        ssf.c VLFS patch 08/1/96