Database Administrator

Hive MapJoin Mechanism What is MapJoin?MapJoin, as its name implies, is the connection between tables in the Map stage. The connection does not need to enter the Reduce stage. This saves a lot of data transmission in the Shuffle phase. Thus it plays

MySQL master replication + Keepalived to create a highly available MySQL Cluster In response to the company's needs, we have created a safer mysql cluster to implement mysql failover. After several days of research, we can finally share the results.

Use GoldenGate to synchronize data from MySQL to Oracle in real time Use GoldenGate to synchronize data from MySQL to Oracle in real time Step 1: Configure mysqlModify the configuration file my. ini# For goldengateLog-bin = "C:/mysql/logbin.

Explore Character Set problems in Oracle EXP/IMP Process 1. Problem description: Data migration between Oracle databases is a common job. EXP/IMP is a common data migration and conversion tool, because the exported files are platform-independent,

Use cold backup technology to quickly migrate databases to new machines Note:1. Test EnvironmentSYS @ ocp> show relVPC: release 1102000100$ Uname-r 2.6.18-164. el5xenDatabase log mode: No Archive ModeMv or cp after shutdown immediate2. Cold backup

Oracle online extended partitions In the Oracle Partition Table operation, when a partition already has the largest partition, how can we expand the partition again? The simple method is to delete the maximum partition first, then add the required

Introduction to common Oracle data dictionaries A data dictionary is a group of tables and view structures in which Oracle stores information about database objects. It is used to describe data. For example, the Creator information, creation time

Feedback settings in SQLPLUS When SQL plus is used to execute an SQL statement, a prompt such as "XX rows have been returned" may be returned for the result returned by a SELECT statement, but this prompt is not found when a database is opened

ORA-12516 TNS: Listeners cannot find available handlers that meet protocol stack requirements Problem scenario: A previous database was used for testing (department A). Last night, another test department (Department B) came to test the program.

Oracle parameter file Introduction After the Oracle database is started, you can use the select * from v $ parameter statement to view all the parameters used by the Oracle database. Oracle parameter files are divided into spfile binary files and

Relationship between Oracle instances and databases Databases are physical and physical storage of data. They consist of files stored on disks, including control files, data files, and redo log files; The instance is logical and consists of the

Use flashback to view historical Oracle table time data Use flashback to view historical Oracle table time data 1. View historical table time data Select * from tab_test as of timestamp to_timestamp ('2014 10:00:00 ', 'yyyymmdd hh24: mi: ss '); 2

Brief Analysis of Oracle execution plan 1. How to open the execution plan: Turn on the Execution Plan (execute set autotrace traceonly/off) and if you are prompted for a SP2-0611, SP2-0618, follow these steps to create the appropriate user. 1. log

Configure DataGuard to report to ORA-12528 (In the creation of DataGuard, run rman recovery error ORA-12528 error; The script is as follows: RMAN> connect auxiliary sys/Oracle @ SCMPRD02 Solution: 1. Check whether the listener is started. Script:

Reflection on ORA-00020 Check the alert Log in the production environment today and find the following error. This error does not need to be explained too much. Obviously, this is because of the classic problem of session leak. ORA-00020: maximum

Oracle implements function-based indexing Use Cases:When a query runs slowly. By checking the where clause, it is found that the SQL lower function is applied to a column, and the lower function prevents the use of existing indexes on the column.

Problems caused by inconsistent Oracle field type design and actual business During the design of the Oracle table, developers always disagree with the field type. The following example shows how to design the field as number and the result is

Oracle imports data to another database through the data pump network without generating DMP files This document records an Oracle Data Import experience for future review. Because the project needs to import the database (USER1) on server A to the

Primary Key considerations for Database Design According to the second paradigm, primary keys are required. The primary key is still unique, and the primary key is also referenced as a foreign key to establish the relationship between the table and

Objects in ADO. NET: Connection, Command, DataReader, DataAdapter, DataSet, and able, It may be because I didn't make a good summary at the beginning. NET. objects in. NET have been vague. Today, I reviewed them again. I checked the information,