Database Administrator

1.Back up databaseConcept: it refers to backing up all data files and control files of the database, and also backing up parameter files and password files.Note: When backing up a database, do not back up redo logs.1.1Consistent backupConcept:

The customer has encountered a problem with DG. The storage uses ASM management and has multiple disk disks.When a data file is created in the master database, the data files automatically created in the slave database are in the same disk group,

NoSQL Database: consistent reading of data High ConsistencyAccess any node in the cluster at any time, and the data obtained is consistent; User consistencyFor the same user, the data obtained during cluster access is consistent;Solve user

The following error occurs during DG switching:   ORA-00274: illegal recovery option SEESION   Problem description: When I run the switch statement on the master database and then switch the slave database to the master database, this problem occurs:

I. fault description First, the REDO file required for instance recovery is damaged. Ii. Solution 1. Use the following CLEAR command for non-current REDO or current REDO but no active transactions: Use the CLEAR command to recreate the log file SQL>

-- User SQL> -- create a user named "grace" whose password is password. The new user does not have any permissions. SQL> create user grace identified by password; Verify the user: password Authentication Method (User Name/password) external

In MySQL, we can store a value or a user-defined variable saved in a query result, and then apply the following statement.SET defines the variable; SET @ var_name: = expr [, @ var_name = expr]...SET @ var_name = expr [, @ var_name = expr]...Note:① ":

Uml-Unified Modeling Language, called the Unified Modeling Language, is a visual Modeling Language used to design software blueprints. It supports the analysis, design, implementation and delivery of object-oriented systems, and supports system

EF provides the function of updating some data of an object while retaining other data. 1. Re-instance an object and give the ID and fields to be modified. Note: The entity here cannot be queried from the database, but can only be a new instance.

Next, REDO error after the OPEN Database and the error ORA-00600: internal error code, arguments: [2662]. The reason is _ allow_resetlogs_uption after resetlogs open the database, we may encounter ORA-00600 2662 error due to inconsistent SCN, here

N + 1 Problems N + 1 is the most common performance problem in database access. First, let's introduce what N + 1 is: For example, there are two tables in our database: MERs and Orders. Orders contains a foreign key mermer_id pointing to the

A friend asked a question in the QQ group two days ago. The background is as follows: After continuing to ask, I have the following reply: 1. The connection to the other server is normal. 2. The slave client can telnet port 1521 of the server. 3.

Building oracle11G DG in linux (III): Building a slave Database Environment Name Master Database Slave Database Host Name Bjsrv Shsrv Software Version RedHat performanise5.5, Oracle 11g 11.2.0.1 RedHat

In the process of using MySQL DATA, sometimes we need a field that is not the primary key and does not repeat it. In this case, we need to use the SQL UNIQUE constraint. The following is an introduction from w3school: The UNIQUE constraint

Database: Oracle11gr2 Master DatabaseAlter database force logging;Alter system set db_unique_name = 'erpdb' scope = spfile; -- let's make the master database db_name = db_unique_nameAlter system set REMOTE_LOGIN_PASSWORDFILE = EXCLUSIVE scope =

Building oracle11G DG in linux (4): subsequent verification Environment Name Master Database Slave Database Host Name Bjsrv Shsrv Software Version RedHat performanise5.5, Oracle 11g 11.2.0.1 RedHat

33.You want to create an ORD_DETAIL table to store details for an order placed having the following business requirement:1) The order ID will be unique and cannot have null values.2) The order date cannot have null values and the default shocould be

Row_number () OVER (partition by COL1 order by COL2)-- Indicates grouping by COL1 and sorting by COL2 within the group, and the value returned by this function indicates the sequential number after sorting within each group (the continuous and

1. What is Oracle Before learning the DRP system, I have mentioned Oracle many times and learned about it. What is Oracle? Today, I finally unveil its secrets. Oracle: A company. Of course, I am talking about Oracle databases here. Like SQL server,

32. Which create table statement is valid?A. create table ord_details(Ord_no NUMBER (2) primary key,Item_no NUMBER (3) primary key,Ord_date date not null ); B. CREATE TABLE ord_details(Ord_no NUMBER (2) UNIQUE, not null,Item_no NUMBER (3 ),Ord_date