oracle数据库在实时监控sql性能时怎么筛选那些没有索引的，性能差的sql语句，需要实时的，最好能自主选择一段时间的
SELECT sql_text, executions,
ROUND(disk_reads / executions, 2) reads_per_run,
disk_reads, buffer_gets,
ROUND((buffer_gets - disk_reads)
/ buffer_gets, 2) hit_ratio,
sql_text
FROM v$sqlarea
WHERE executions > 0
AND buffer_gets > 0
AND (buffer_gets - disk_reads) / buffer_gets < 0.80
ORDER by 3 desc ;
//性能最差的SQL
SELECT * FROM ( SELECT PARSING_USER_ID EXECUTIONS,SORTS,COMMAND_TYPE,DISK_READS,sql_text
FROM v$sqlarea
ORDER BY disk_reads DESC)
WHERE ROWNUM<100;