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- 低命中率:
- SQL> SELECT NAME, PHYSICAL_READS, DB_BLOCK_GETS, CONSISTENT_GETS,1 - (PHYSICAL_READS / (DB_BLOCK_GETS + CONSISTENT_GETS)) "Hit Ratio" FROM V$BUFFER_POOL_STATISTICS WHERE NAME='DEFAULT';
- NAME PHYSICAL_READS DB_BLOCK_GETS CONSISTENT_GETS Hit Ratio
- --------------------------------------------- -------------- ------------- --------------- ----------
- DEFAULT 6210720328 1.4327E+10 1.2043E+10 .764479736
- SQL> SELECT a.VALUE + b.VALUE logical_reads,
- c.VALUE phys_reads,
- round(100 * (1 - c.value / (a.value + b.value)), 4) hit_ratio
- FROM v$sysstat a, v$sysstat b, v$sysstat c
- WHERE a.NAME = 'db block gets'
- AND b.NAME = 'consistent gets'
- AND c. 2 3 4 5 6 7 NAME = 'physical reads';
- LOGICAL_READS PHYS_READS HIT_RATIO
- ------------- ---------- ----------
- <div> 3.3504E+10 1.3451E+10 59.8542</div><div>
- </div><div>
- </div><div>参数:</div><div>SQL> show sga
- Total System Global Area 3240239104 bytes
- Fixed Size 2217712 bytes
- Variable Size 2483030288 bytes
- Database Buffers 738197504 bytes
- Redo Buffers 16793600 bytes
- SQL> show parameter sga
- NAME TYPE VALUE
- ------------------------------------ ----------- ------------------------------
- lock_sga boolean FALSE
- pre_page_sga boolean FALSE
- sga_max_size big integer 3104M
- sga_target big integer 0
- SQL> show parameter cache_size
- NAME TYPE VALUE
- ------------------------------------ ----------- ------------------------------
- client_result_cache_size big integer 0
- db_16k_cache_size big integer 0
- db_2k_cache_size big integer 0
- db_32k_cache_size big integer 0
- db_4k_cache_size big integer 0
- db_8k_cache_size big integer 0
- db_cache_size big integer 0
- db_flash_cache_size big integer 0
- db_keep_cache_size big integer 0
- db_recycle_cache_size big integer 0</div>
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今天巡检发现,这两个的命中率都是低于95%,请问各位大大这种问题应该怎么分析,需要调整什么参数吗?
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