(1)lc的命中率:
.計算公式:library cache hit ratio = sum(pinhits) / sum(pins)
selectsum(pinhits)/sum(pins)fromv$librarycache
通常在98%以上，否則，需要要考慮加大共享池，繫結變數，修改cursor_sharing等引數。
.計算共享池記憶體使用率:
select(1-round(bytes/(&tsp_in_m*1024*1024),2))*100||'%'fromv$sgastatwherename='free memory'andpool='shared pool';
其中: &tsp_in_m是你的總的共享池的size(m)
共享池記憶體使用率，應該穩定在75%-90%間，太小浪費記憶體，太大則記憶體不足。
查詢空閒的共享池記憶體:
select*fromv$sgastatwherename='free memory'andpool='shared pool';
(2)pga的命中率:
計算公式:bp x 100 / (bp + ebp)
bp:bytes processed
ebp:extrabytesread/written
select*fromv$pgastatwherename='cache hit percentage';
或者從oem的圖形介面中檢視
我們可以檢視乙個檢視以獲取oracle的建議值:
select round(pga_target_for_estimate/1024/1024) target_mb,
estd_pga_cache_hit_percentage cache_hit_perc,
estd_overalloc_count
from v$pga_target_advice;
the output of this query might look like the following:
target_mb cache_hit_perc estd_overalloc_count
63 23 367
125 24 30
250 30 3
375 39 0
500 58 0
600 59 0
700 59 0
800 60 0
900 60 0
1000 61 0
1500 67 0
2000 76 0
3000 83 0
4000 85 0
在此例中:pga至少要分配375m
我個人認為pga命中率不應該低於50%
以下的sql統計sql語句執行在三種模式的次數: optimal memory size, one-pass memory size, multi-pass memory size:
select name profile, cnt, decode(total, 0, 0, round(cnt*100/total,4)) percentage
from (select name, value cnt, (sum(value) over ()) total from v$sysstat where name like 'workarea exec%');
計算在記憶體中排序的比率:
select * from v$sysstat t where name='sorts (memory)'—查詢記憶體排序數--select * from v$sysstat t where name='sorts (disk)'—查詢磁碟排序數--caculate sort in memory ratioselect round(&sort_in_memory/(&sort_in_memory+&sort_in_disk),4)*100||'%' from dual
此比率越大越好,太小整要考慮調整,加大pga
(3)db buffer cache命中率:
計算公式:hit ratio = 1 - [physical reads/(block gets + consistent gets)]
select name, physical_reads, db_block_gets, consistent_gets,
1 - (physical_reads / (db_block_gets + consistent_gets)) "hit ratio"
from v$buffer_pool_statistics
where name='default';
通常應在90%以上，否則，需要調整,加大db_cache_size
另外一種計算命中率的方法(摘自oracle官方文件<>):
select name, value
from v$sysstat
where name in('session logical reads',
'physical reads',
'physical reads direct',
'physical reads direct (lob)',
'db block gets', 'consistent gets');
命中率的計算公式為:hit ratio = 1 - ((physical reads - physical reads direct - physical reads direct (lob)) /
(db block gets + consistent gets - physical reads direct - physical reads direct (lob))
分別代入上一查詢中的結果值,就得出了buffer cache的命中率
幾個常用的檢查語句
1.查詢排序最多的sql:
select hash_value, sql_text, sorts, executions
from v$sqlarea
order by sorts desc;
2.查詢磁碟讀寫最多的sql:
select * from
(select sql_text,disk_reads "total disk" ,
executions "total exec",disk_reads/executions "disk/exec" from v$sql where executions>0
and is_obsolete='n' order by 4 desc)
where rownum<11
3.查詢工作量最大的sql(實際上也是按磁碟讀寫來排序的):
selectsubstr(to_char(s.pct, '99.00'), 2) || '%' load,s.executions executes,p.sql_textfrom(selectaddress,disk_reads,executions,pct,rank() over (order by disk_reads desc) rankingfrom(selectaddress,disk_reads,executions,100 * ratio_to_report(disk_reads) over () pctfromsys.v_$sqlwherecommand_type != 47)wheredisk_reads > 50 * executions) s,sys.v_$sqltext pwheres.ranking <= 5 andp.address = s.addressorder by1, s.address, p.piec 4.用下列sql工具找出低效sql:select executions , disk_reads, buffer_gets,
round((buffer_gets-disk_reads)/buffer_gets,2) hit_radio,
round(disk_reads/executions,2) reads_per_run,
sql_text
from v$sqlarea
where executions>0
and buffer_gets > 0
and (buffer_gets-disk_reads)/buffer_gets < 0.8
order by 4 desc;
redis命中率計算
redis提供了info這個命令，能夠隨時監控伺服器的狀態，只用telnet到對應伺服器的埠，執行命令即可 telnet localhost 6379 info在輸出的資訊裡面有這幾項和快取的狀態比較有關係 keyspace hits 14414110 keyspace misses 3228654...
redis命中率計算
redis提供了info這個命令，能夠隨時監控伺服器的狀態，只用telnet到對應伺服器的埠，執行命令即可 quote telnet localhost 6379 info quote 在輸出的資訊裡面有這幾項和快取的狀態比較有關係 quote keyspace hits 14414110 keys...
Redis命中率計算
redis提供info命令，能夠隨時監控伺服器的狀態，只用telnet到對應伺服器的埠，執行命令即可 telnet localhost 6379 info在輸出的資訊裡面有這幾項和快取的狀態比較有關係 keyspace hits 14414110 keyspace misses 3228654 us...