Database Administrator

Kfed and kfod in CRS_HOME/bin are very useful tools for checking ASM disk. -Bash-2.05b $ kfed-helpAs/mlib ASM Library [asmlib = 'lib']Aun/um AU number to examine or update [AUNUM = number]Aus/z Allocation Unit size in bytes [AUSZ = number]Blkn/um

1. Use the trace file to restore SQL> alter database backup controlfile to trace; -- back up the control file to the trace file Database altered. SQL> @ gettrace -- get the path of the trace file TRACE_FILE_NAME---------------------------------------

I. Environment Description (using rsync for mysql Incremental Backup) 192.168.0.2 is the backup server. 192.168.0.3 is the mysql database that needs to be backed up frequently. Ii. Main Configuration 1. Backup Server ConfigurationUseradd

This is a foreign article that elaborates on the differences between the two open-source databases MySQL and PostgreSQL in seven aspects. These seven aspects include: Architecture Performance ACID transactions Features Authorization

If a Cache clause is specified when a table is created or modified, the table will be added to the database Cache for a long time when the data in the table is accessed for the first time, in this way, the user can access the table again, and can

1 Definition RBA is the address corresponding to redo entries in the redo log file. 2 components RBA consists of three parts: Serial number (4 bytes) Block number (4 bytes) Start byte (2 bytes) All of the above are in hexadecimal storage. 3 type 3.1

Character Functions This function generally receives characters as parameters and can return characters or numbers. The following two functions are commonly used: 1. CONCAT Function It is mainly used for string connection. The specific syntax is as

For Oracle 11gR2 RAC best practices for adding nodes, see:OS information:[Grid @ 11grac1 ~] $ Uname-Linux 11grac1 2.6.32-300.10.1.el5uek #1 SMP Wed Feb 22 17:22:40 EST 2012 i686 i686 i386 GNU/LinuxDB information:SQL> select * from v $ version where

The Hash Index is based on the Hash table. It is only useful for exact search of each column in the Index. For each row, the storage engine calculates the indexed Hash Code, which is a small value and may be different from the Hash Code of other

Mysql usually does not use an index if no indexed columns are isolated in the query. "Isolation" column means it is not part of the expression and is not in the function. For example: Mysql> select id from test where id + 1 = 5; We can easily see

Oracle does not have auto-incrementing primary keys like Mysql and SQLSERVERHowever, you can use other methods to replace the automatic primary key method, including sequence creation and trigger creation.Here we will focus on sequence

FlashbackFlash back is divided into three categories First,Flashback table Second,Flashback database Third,Flashback query (I), Enable and disable the recycle bin Alter session setrecyclebin = on; Altersession set recyclebin = off; Altersystem set

System not only has the permissions of the DBA role, but also has other permissions. Use sys userAuthorizeThe related permissions are found in the dba_role_privs table.Select t. GRANTED_ROLE FROM DBA_ROLE_PRIVS t where t. GRANTEE = 'system ';There

For the strange data, the value of select is obviously 0.0140625, but it is not rounded down by round (vv, 6. It should be calculated as follows: 0.014063, but the actual result is: 0.014062. It violates the rounding principle. Case: Drop table

At work, a table inserts a lot of data every day, and the amount of data will become larger than millions or even tens of millions of records over time. In this case, can we split the table? The answer is that Oracle has provided a horizontal split

Basic concepts of a package A package can organize several functions or stored procedures and store them as an object. A package usually consists of two parts: specification and body ). The program reports can also contain constants and variables.

When I interviewed mysqldba, I encountered a question: Describes the implementation principle of the msyql replication mechanism. How can I restore the database node of the slave with inconsistent data without stopping the mysql master

1. Control File: a binary file that records the physical structure of the database.2. The control file mainly includes:Database Name (DB_NAME)Data file name, and location, REDOLOG file name and locationDatabase creation timeCurrent Log SCNCHECKPOINT

MySQL Stored Procedure array implementation: DELIMITER $ Drop procedure if exists 'array' $ Create procedure 'array '() BEGIN SET @Array_content="Www mysql com hcymysql blog 51cto com"; SET @I=1; SET @Count=CHAR_LENGTH(@

The InnoDB Storage engine of MySQL not only caches indexes, but also caches data. If you store tables and indexes on Raw devices, by bypassing the file system's high-speed cache and buffer, direct access to the disk will greatly reduce the burden on