Database Administrator

Test environment: MySQL 5.0.45 [Note: You can use MySQL> select version (); in mysql to view the database VERSION] 1. Connect to MySQL. Format: mysql-h host address-u user name-p User Password 1. Connect to MySQL on the local machine. First open the

The VM for Linux prefers system cache over application memory. What does this mean? The best way I can explain is by example. Imagine you have 32 GB of RAM MySQL is set to take 20 GB of RAM for a process based buffer and up to 6 M for the varous

1. type conversion functions: decimal, double, Integer, smallint, real, Hex (arg ), Date, time, timestamp, char, varchar Common examples: -- Convert to string type Oracle: select to_char (15.5000) from dual; DB2: select char (15.5000) from sysibm.

You can choose from two solutions: 1. Use the database upgrade assistant (dbua) upgrade utility provided by oracle to directly upgrade 9i database to 10 Gb. 2. Create a 10 Gb database and use the import/export (imp/exp) utility of oracle to migrate

Method 1:Under/usr/local/mysql/bin:./Mysqladmin-u root password 'new _ password'This method is usually used for installation. Method 2:In mysql:Mysql> UPDATE user SET password = PASSWORD ('new _ password') WHERE user = 'root ';Mysql> flush

CentOS mysql has been widely used but is constantly updated. Here we will introduce how to install and use CentOS mysql to help you install and update CentOS mysql. Install CentOS mysql; 1] Extract[Root @ localhost root] #

1. Connection The default mongodb port is 27017. Therefore, we can connect to mongodb: $ mongodb = new Mongo ('localhost') or specify the IP address and port $ mongodb = new Mongo ('192. 168.127.1: 27017 ') the port can be changed. If mongodb

-- According to friends, the performance improvement is obvious after DNS is turned off.-- The mysql. cnf file is in/ect/init. d/mysql. cnf.Recently, I found that two MySQL servers suddenly went viral at noon (suddenly) and kept failing. Restarting

Use the built-in functions of mysql: INET_ATON (expr)Given the dotted-quad representation of a network address as a string, returns an integer that represents the numeric value of the address. Addresses may be 4-or 8-byte addresses.Mysql> SELECT

I. background of testing requirements1. Have you asked me if the initialization parameter can take effect immediately after modification? I did a test immediately and concluded that yes. 2. in linux, Oracle data blocks are 8 KB by default and

Today I saw a little questions about ocp, I did a small experiment, encountered two errors of ORA-02097 and ORA-00837; Question: Q484. You set the following parameters in the parameter fileand restarted the database: MEMORY_MAX_TARGET =

Compared with physical Standby, logical Standby management is a little more complicated. This is the difference between one half database management and two databases (assuming that the Data Guard environment is one master and one slave). After all,

Resolving Oracle listener startup errors 1, TNS-12547: TNS-12547: TNS: lost contactTNS-12560: TNS: protocol adapter errorTNS-00517: Lost contactLinux Error: 104: Connection reset by peer No 127.0.0.1 localhost is found in/etc/hosts. Modify/etc/hosts

1. Oracle multi-Table query Multi-Table query refers to queries based on two or more tables or views. Question: Display employee name, employee salary, and department name [Cartesian set ]? Select t. ename, t. sal, t1.dnamefrom emp t, dept t1where t.

Preface: We know there are three ways to call the Data Pump. Here, I will never use the command line but the first script method. The reasons for dropping the command line are as follows: ① Operating system restrictions on the number of CLI

Oracle provides three standard roles (role) for compatibility with earlier versions: connect, resource, and dba. 1. connect role (connection role) Temporary users, especially those who do not need to create tables, usually only connect them. Connect

Because the addition, deletion, and modification of the MySQL database suddenly increase, the operations on the tables that need to be queried are very frequent. I wrote a small tool to analyze the bin-log and find the tables for addition, deletion,

Start Oracle of the VM and execute startup. the following error code is displayed, SQL> startup ORA-00119: invalid specification for system parameter LOCAL_LISTENERORA-00130: invalid listener address '(ADDRESS = (PROTOCOL = TCP) (HOST = orapy) (PORT

These three table join methods are the most basic connection methods for Oracle:Principle of nested loop joinPrinciple of sortmerge join Hashjoin) Number of visits: both the driver table and the driver table can only be accessed 0 times or

In the case of network transformation, You need to modify the name or IP address of the database server. This will affect the normal operation of the Oracle database, because the listener and many database tools need the correct machine name or IP