unable to run gather statistics in our database

Dear All,
Im  getting below error msg as while i running dbms_stats package.

SQL> EXEC DBMS_STATS.gather_database_stats;
BEGIN DBMS_STATS.gather_database_stats; END;

*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified
ORA-06512: at "SYS.DBMS_STATS", line 13591
ORA-06512: at "SYS.DBMS_STATS", line 13937
ORA-06512: at "SYS.DBMS_STATS", line 14081
ORA-06512: at "SYS.DBMS_STATS", line 14045
ORA-06512: at line 1

Pls help me.

Thanks,