Physical Reads通常是我们最关心的,如果这个值很高,说明要从磁盘请求大量的数据到Buffer Cache里,通常意味着系统里存在大量全表扫描的SQL语句,这会影响到数据库的性能,因此尽量避免语句做全表扫描,对于全表扫描的SQL语句,建议增 加相关的索引,优化SQL语句来解决。 关于physical reads ,db block gets 和consistent gets...
Oracle Database generates an internal SQL statement, which in turn generates a recursive call. In short, recursive calls are basically SQL performed on behalf of your SQL. So, if you had to parse the query, for example, you might have had to run some other queries to get ...
Oracle Database generates an internal SQL statement, which in turn generates a recursive call. In short, recursive calls are basically SQL performed on behalf of your SQL. So, if you had to parse the query, for example, you might have had to run some other queries to get ...
Physical Reads通常是我们最关心的,如果这个值很高,说明要从磁盘请求大量的数据到Buffer Cache里,通常意味着系统里存在大量全表扫描的SQL语句,这会影响到数据库的性能,因此尽量避免语句做全表扫描,对于全表扫描的SQL语句,建议增 加相关的索引,优化SQL语句来解决。 关于physical reads,db block gets和consistent gets这...
SQL>SELECTname, valueFROMv$sysstatWHEREnameIN(\'db block gets\',\'consistent gets\',\'physical reads\'); 查询出来的结果Buffer Cache的命中率应该在90%以上,否则需要增加数据缓冲区的大小。 清空Buffer Cache和数据字典缓存 SQL> alter system flush shared_pool;//请勿随意在生产环境执行此语句System alter...
SQL>SELECT plan_table_output FROM TABLE(DBMS_XPLAN.DISPLAY('PLAN_TABLE')); 或者: SQL>select * from table(dbms_xplan.display); PLAN_TABLE_OUTPUT --- Plan hash value: 3458767806 --- | Id| Operation| Name | Rows| Bytes | Cost (%CPU)| Time| ---...
CJQ0 typically handles job queues for the older DBMS_JOB framework but also plays a part in the execution of DBMS_SCHEDULER jobs by managing the job queue and distributing jobs to job slaves (Jnnn processes) for execution. CQJ0 is related to job scheduling, specifically for Oracle's Scheduler...
EXPLAIN PLAN SET statement_id = 'ex_plan2' FOR SELECT last_name FROM employees WHERE last_name LIKE 'Pe%'; SELECT PLAN_TABLE_OUTPUT FROM TABLE(DBMS_XPLAN.DISPLAY(NULL, 'ex_plan2','BASIC')); --- | Id | Operation | Name | --- | 0 | SELECT STATEMENT | | | 1 | INDEX RANGE ...
>>Note the drop-down control added to the Explain Plan button in the worksheet toolbar. This is a total disaster. Please make an option to disable this “feature” or just disable it. This “feature” blocks using dbms_xplan. I...
[转]Oracle执行计划（ExplainPlan）说明 [转]Oracle执⾏计划（ExplainPlan）说明 原⽂地址:http://langgufu.iteye.com/blog/2158163 如果要分析某条SQL的性能问题，通常我们要先看SQL的执⾏计划，看看SQL的每⼀步执⾏是否存在问题。如果⼀条SQL平时执⾏的好好的，却有⼀天突然性能很差，如果排除了...