When perform "drop tablespace xxx including contents and datafiles",This session occurs HANG with wa

HI,
I have a problem about event wait "row cache lock",It occurs when I performing command “drop tablespace xxx including contents and datafiles"

This session hold sql_id is 000000000

Below line is the informations that I checked.

SQL> select p1text,p1,p2text,p2,p3text,p3 from v$session where event = 'row cache lock';
P1TEXT        P1 P2TEXT       P2       P3TEXT         P3
---------------------------------------------------------------- ----------
cache id      2  mode          0        request        5


SQL> select parameter,count,gets,getmisses,modifications from v$rowcache where cache#=5;

PARAMETER                             COUNT       GETS  GETMISSES MODIFICATIONS
-------------------------------- ---------- ---------- ---------- -------------
dc_tablespace_quotas                      2    8381983     318689       3952217


SQL> column pct_succ_gets format 999.9