28-1:
	exec dbms_stats.gather_table_stats('scott','emp')
28-2:
	SELECT num_rows,avg_row_len,blocks,chain_cnt,avg_space FROM user_tables WHERE table_name='EMP';
28-3:
	SELECT num_distinct,num_nulls,avg_col_len FROM user_tab_col_statistics WHERE table_name='EMP' AND column_name='COMM';
28-4:
	exec dbms_stats.delete_table_stats('scott','emp')
28-5:
	exec dbms_stats.gather_index_stats('scott','pk_emp')
28-6:
	SELECT num_rows,blevel,leaf_blocks,clustering_factor FROM ind WHERE index_name='PK_EMP';
28-7:
	exec dbms_stats.delete_index_stats('scott','pk_emp')
28-8:
	exec dbms_stats.gather_table_stats('scott','emp',method_opt=>'FOR COLUMNS deptno SIZE 3')
28-9:
	SELECT endpoint_number,endpoint_value FROM user_histograms WHERE table_name='EMP' AND column_name='DEPTNO';
28-10:
	exec dbms_stats.gather_schema_stats('scott')
	exec dbms_stats.delete_schema_stats('scott')
28-11:
	conn system/manager
	exec dbms_stats.gather_database_stats
	exec dbms_stats.delete_database_stats
28-12:
	exec dbms_stats.gather_system_stats('START')
	exec dbms_stats.gather_system_stats('STOP')
28-13:
	CREATE OR REPLACE FUNCTION stat_val(pname VARCHAR2) RETURN NUMBER
	IS
	  status VARCHAR2(20);
	  dstart DATE;  dstop DATE;
	  pvalue NUMBER(15,4);
	BEGIN
	  dbms_stats.get_system_stats(status,dstart,dstop,pname,pvalue);
	  RETURN pvalue;
	END;
	/
	exec dbms_output.put_line(stat_val('sreadtim'))
	exec dbms_output.put_line(stat_val('cpuspeed'))






