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大数据管理
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HugePage-大页空间深度解析
内存标准页大小是4k，对于内存使用较多，访问内存又比较分散的场景，4k的页大小会导致页表（每个进程一个，用于索引内存物理地址）很大，cpu高速缓存又很小，会导致大量的页表项无法被高速
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MySQL执行计划初探
执行计划收集DAO_OBJECTS t1 , DAO_OBJECTS t2 WHERE deptno= t1.object_id AND t1.object_name=t2.object_name ;+----+-------------+-------+------+--------------
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ORA-00025: failed to allocate string
ORA-00025: failed to allocate string
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ORA-00024: logins from more than one process not allowed in single-process mode问题的原因和处理方法
ORA-00024: logins from more than one process not allowed in single-process modeCause: Trying to login more than once from different processes for ORACLE started
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ORA-00023: session references process private memory;问题的原因和处理方法
ORA-00023: session references process private memory; cannot detach sessionCause: An attempt was made to detach the current session when it contains references
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ORA-00022: invalid session ID; access denied问题的原因和解决方法
ORA-00022: invalid session ID; access deniedCause: Either the session specified does not exist or the caller does not have the privilege to access it.Action: Sp
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ORA-00021: session attached to some other process; cannot switch session问题的原因及处理方法
ORA-00021: session attached to some other process; cannot switch sessionCause: The user session is currently used by others.Action: Do not switch to a session a
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ORA-00020: maximum number of processes (string) exceeded问题的原因和处理方法
ORA-00020: maximum number of processes (string) exceededCause: All process state objects are in use.Action: Increase the value of the PROCESSES initialization p
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ORA-00019: maximum number of session licenses exceeded问题的原因和处理方法
ORA-00019: maximum number of session licenses exceededCause: All licenses are in use.Action: Increase the value of the LICENSE MAX SESSIONS initialization param
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ORA-00018: maximum number of sessions exceeded问题的原因和处理方法
ORA-00018: maximum number of sessions exceededCause: All session state objects are in use.Action: Increase the value of the SESSIONS initialization parameter.OR
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ORA-00017: session requested to set trace event问题的原因和处理办法
ORA-00017: session requested to set trace eventCause: The current session was requested to set a trace event by another session.Action: This is used internally;
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ORA-00001: unique constraint (string.string) violated问题的原因与处理办法
ORA-00001: unique constraint (string.string) violatedCause: An UPDATE or INSERT statement attempted to insert a duplicate key. For Trusted Oracle configured in
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Oracle隐含参数速查
Oracle隐含参数速查
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Oracle 脚本-查看失效对象信息
select owner , 2 object_name , 3 object_type 4 from dba_objects 5 where status ='INVALID' 6 order by 1,2,3 ;OWNER OBJEC
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Oracle 脚本-查看日志文件写平均等待事时间
```sqlSQL> select total_waits, 2 time_waited, 3 average_wait, 4 time_waited / total_waits as avg_time 5 from v$system_eve
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Oracle 脚本-查看平均每秒事务数
```sqlSQL> select (select sum(to_number(value, 99999999999)) 2 from v$sysstat 3 where name in ( 'user rollbacks','user commits') )/ 4
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Oracle 脚本-查看每秒回滚次数
```sqlSQL> select (select to_number(value, 99999999999) 2 from v$sysstat 3 where name = 'user rollbacks') / 4 (select (sysdate -
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Oracle 脚本 -查看当前数据库启动多久
```sqlSQL> select (sysdate - startup_time) * 24 start_hour 2 from v$instance ;START_HOUR---------- 60.19```
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Oracle 脚本 -查询实例平均每秒提交次数
```sqlSQL> select (select to_number(value, 99999999999) 2 from v$sysstat 3 where name = 'user commits') / 4 (select (sys
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Oracle 脚本-查看临时表空间使用率
```sqlSQL> SELECT TMP_TBS.TABLESPACE_NAME, 2 SUM(TMP_TBS.TOTAL_MB) TOTAL_MB, 3 SUM(USED_TOT.USED_MB) USED_MB, 4 SUM(USED_TOT.USED_MB)
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Oracle 脚本-查看使用系统表空间作为默认表空间的用户
```sqlSQL> select t.username, 2 t.account_status, 3 t.default_tablespace 4 from dba_users t 5 where t.default_tablespace = 'SYSTEM' ;US
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Oracle 脚本 -查看前十个热点文件
```sqlSQL> SELECT T.FILE_NAME, 2 T.TABLESPACE_NAME, 3 ROUND(S.SINGLEBLKRDTIM / S.SINGLEBLKRDS, 2) AS CS, 4 S.READTIM / 100READTIME_S,
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Oracle 脚本-查看物理读最多的对象
```sqlSQL> select * 2 from(select owner, object_name,value 3 from v$segment_statistics 4 where statistic_name ='physical reads' 5
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Oracle脚本-查看那些用户有DBA权限
```sqlSQL> select * 2 from DBA_ROLE_PRIVS 3 WHERE GRANTED_ROLE = 'DBA' 4 ORDER BY GRANTEE;GRANTEE GRANTED_ROLE ADMIN_OPTION DEFAULT_ROLE--
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Oracle 脚本--查看数据文件临时文件I/O信息
```sqlSQL> select ceil(sum(bytes) / 1024 / 1024 / 1024) FILE_SIZE_GB 2 from (select bytes 3 from v$datafile 4 union all 5 se
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