Tuning “Backup:sbtbackup” Event

A few days ago a friend ask me to see a awr issue. In t […]


因一次硬件原因导致了服务器异常停机,防止蝴蝶效应及时进行了数据迁移,一周发现了这个决定正确的。 申请了2小时的 […]

About ORACLE CPU, PSU, SPU Patch Nomenclature

It all started in January 2005 with Critical Patch Updates (CPU). Then Patch Set Updates (PSU) were added as cumulative patches that included priority fixes as well as security fixes.

Backup ASM metadata with shell

Creates a backup directory if required, works out the A […]

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linux发送手机短信 利用fesion robot



Tuning “Read by other session wait” Event

This wait event occurs when we are trying to access a buffer in the buffer cache but we find that the buffer is currently being read from disk by another user so we need to wait for that to complete before we can access it.


客户要求导出大量的数据(约800万记录),开始为了格式上的好看生成的是ACCESS数据库文件,用Toad 11 […]

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Tuning ‘log file sync’ Event

The log file sync wait occurs at the end of a transaction (COMMIT or End Of Job)and the database writer (DBWR) process must wait for the log file to synchronize with the database.

Tuning ‘latch: row cache objects’ Event

This latch comes into play when user processes are attempting to access or update the cached data dictionary values.


ORA-00600 [qkssao2s1] internal error issue

ORA-00600: internal error code, arguments: [ORA-00600: internal error code, arguments: [qkssao2s1], [], [], [], [], [], [], []

SQL hint mean force? More about parallel(二)(不并行的场景)

sql中如果使用了parallel hint 或是force parallel query 想并行查询的特性,如果那样做了就一定能保证 query optimizer选择并行的执行计划么?知道那样做实际上产生什么样的影响么?


More about ITL in oracle

ITL(Interested Transaction List ),The Oracle database engine locks the data modified by a transaction at the row level. To implement this feature every data block contains a list of all transactions that are modifying it. This list is commonly called interested transaction list (ITL).

Oracle GoldenGate Trail File

Trail files are generated by both the original extract and the Data Pump (extract) process. Trail files are read by the Data Pump (extract) and Replicat (replicat) processes

Schema level flashback(闪回用户或方案)

Technically there is no schema level flashback feature […]

Script: Who’s using a database link?(找出谁在使用dblink)

Every once in awhile it is useful to find out which ses […]


More about index


Tuning PGA Memory

You can get the correct size of PGA using V$PGA_TARGET_ADVICE, dynamic performance view.

HAVING expression default Selectivity

In some cases the query optimizer might can not accurately estimate cardinality (e.g. group by having or like with bind variables cause etc..),therefore the Cardinality estimates are based on default seletivity of build-in oracle coredefault seletivity(5%).

oracle forall instructs must be followed by DML

Oracle BULK COLLECT and Oracle FORALL are the new featu […]