Database Administrator

PostgreSQL is a very complex object-relational database management system (ORDBMS). It is also currently the most powerful, feature-rich and complex free software database system. Some features are not even available in commercial databases. This

Obtaining the Oracle SQL Execution Plan and viewing the execution plan are the basic skills to master and judge the database performance. The following example describes how to view SQL Execution plans: There are basically the following methods: 1.

Today, we used to import all the information from one Oracle user to another. For example, if one user on one machine is aa, all information of the aa user, such as tables, tablespaces, and indexes, needs to be copied to the local database on

The UTL_FILE package can be used to read and write text files on the operating system. UTL_FILE provides file access functions on the client (FORM, etc.) and on the server. Create a test directory: Create a new command window; Create a directory:

In 2013, IBM DB2 was 30 years old and was released in DB2 10.5. One of the most eye-catching features was the BLU accelerator, which introduced columnar storage technology into traditional databases, currently, BLU only supports databases of DB2

1. The Oracle 10g rac server is configured with 128G memory, and the sga pga is very large. After restart, it is found that ipcs show sga is correct, that is, free-m is incorrect, and the difference is very long. 2. You can configure hugepage, but

Oracle bug Document ID 549781.1 Versions affected from 10.2.0.2.0 to 11.2.0.3.0 An error is reported, but the expdp log indicates that the operation is successful. oracle indicates that the exported dmp file is good. This error can only be ignored

The syntax for querying the total number of records in a table is select count (*) FROM TABLE_NAME. This may be the most frequently used type of SQL statements. This article discusses how to obtain the maximum number of records. This article is

PostgreSQL supports hstore to store data such as KEY-> VALUE, which is also similar to ARRAY or JSON. To use this type of data efficiently, you must use efficient indexes. Let's take a look at the performance of two different types of indexes for

Connect to the SUSE Linux service through ssh. Command for setting system time:, January 1 Date -- set = "04/01/14" Step 1: Start the listener;Su-Oracle -- "switch to oracle user"Lsnrctl start -- "enable listener"Step 2: Start the database instance.

For frequent index update, the delete operation produces index Frag, which affects index efficiency and increases index IO. 1. Index fragmentation analysisTest Index fragmentation:SCOTT @ devcedb> select count (*) from obj;COUNT

Server 1 OS: AIX 5.3 Ip: 192.168.0.1 Db: Oracle 11gR2 Server 2: OS: AIX IP: 192.168.0.5 Db: DB2 v9.7 Main purpose: By building a transparent gateway in Server 1, you can connect to the DB2 database in Server 2 in the oracle database. Oracle --->

When exp exports data, the output log reports the EXP-00091: Exporting questionable statistics error, especially for some exp scripts executed in crontab. The cause of this error is that the export end nls_lang parameter is not set, or the setting

-- Problem: query the average salary of each department's position And display it in a query   Idea: first, we will find out the three tables, assuming a B c, and then combine a B with each other. There is no relationship between them, so to

Processing of date fields in Oracle The start_date field exists in the Test table. How can we obtain the year of start_date. For example, start_date is ". The obtained year should be 2014. If the data type of start_date is date. SELECT TO_CHAR

The principle of consistent read is that the query record is determined by the time point of the query. Even if the query record changes later, the data at that point should be obtained based on the pre-image record of rollback and persistence. How

Ubuntu MySQL automated installation script #/Bin/bashFunction hasDpkg{R = 'dpkg-l | grep "$1 "'If [-n "$ r"]ThenH = 'dpkg-l | grep "ii $1 "'If [-n "$ h"]ThenReturn 1ElseReturn 0FiElseReturn 0Fi} Mysql = mysql-server-5.5"HasDpkg $ mysql R = $?If [$ r-

One day, after the machine was restarted due to power failure and insufficient UPS power supply, it was found that the listener could not be started and an error was prompted: TNSLSNR for Linux: Version 10.2.0.1.0-ProductionSystem parameter file

In Versions later than 11.2, crs is called gi. It is very convenient to use crsctl stop cluster to shut down the resources of the entire instance, but the database instance needs to be closed separately, stop cluster ends an instance in an abnormal

As a hotbackup tool of innodb, xtrabackup is developed by percona and widely deployed in mysql due to open source, hot backup, and physical backup. The details can be found in the previous discussions. MySQL management-using XtraBackup for Hot