Database Administrator

Here I will only briefly introduce these two commands, but they are used in the process of use. So I will mention them here. If you are interested in this, you can search for more introductions. Please share them ~~ A Database Transaction starts

Use case First, let's look at an example: There is a user table User (username VARCHAR (5) character set utf8COLLATE utf8_general_ci ); Record ('username'); and ('username '); Select * from User where username = 'username'; two data items are

1. view temporary tablespace (dba_temp_files view) (v _ $ tempfile view)Select tablespace_name, file_name, bytes/1024/1024 file_size, autoextensible from dba_temp_files;Select status, enabled, name, bytes/1024/1024 file_size from v _ $ tempfile; --

Debug a backup script for RMAN today. This script has been used many times before, and there is no problem. When it is executed today, it cannot be used. OS: RedHat 5.8 Database: 11.2.0.3 The error is as follows: RMAN-00571: =========================

Test environment: Install Oracle Enterprise Linux 5.8 64-bit Virtual Machine in VMware Workstation v9.0.2 Install software: jdk-7u40-linux-x64.rpm?apache-tomcat-7.0.53.tar.gz Installation instructions: Download jdk-7u40-linux-x64.rpmand apache-atat-7

In the previous lesson, we talked about how to build a Hadoop environment on a machine. We only configured one NHName Node, which contains all of our Hadoop stuff, including Name Node, secondary Name Node, Job Tracker, and Task Tracker. This section

GridFS is a mechanism for storing large binary files in MongoDB. There are several reasons for saving files with GridFS: Grid can simplify requirements. If you have used MongoDB, GridFS does not need to use an independent file storage

Many Oracle database developers prefer PL/SQL functions, storage, and so on to simplify the code. Recommended reading: Use PL/SQL to execute java storage to obtain the MAC address For example: Select empno, ENAME, DNAME, loc from emp, dept where emp.

There are many locks that can be learned, such as the lock granularity, lock mode, lock compatibility, and isolation level. However, how does one obtain the corresponding lock when running a statement? For example, if a select statement requires an

I didn't expect MongoDB to have so many choices for Node. js drivers! I thought for a while! It turns out that in addition to the Driver found on the MongDB official website, there are also a lot of good people who have written several MongoDB

In the actual operating environment, we often encounter such requirements. For example, if you want to avoid affecting the running time of the DB patch in the current network environment, or, you want to connect to Standby DB for testing of actual

1. To optimize the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order.2. Try to avoid null value determination on the field in the where clause. Otherwise, the engine will discard

Index category: Indexes can be divided into clustered indexes, non-clustered indexes, and unique indexes. Advantages: 1. The main advantage is convenient query and improved system performance. 2. By creating a unique index, You can ensure the

Content Define Collection type Declare Collection variables Initialize and reference Collection Reference Collection Element Assign a value to Collection Multi-dimensional Collection Compare Collection Collection Method Collection

I. Preface Oracle provides PL/SQL developers with a tool to encrypt the code they write (the objects Package, Procedure, Function, and Java Source in oracle. After PL/SQL code is encrypted, it is described as "encapsulated ". Use the wrap tool to

Dataguard is an important solution officially recommended by Oracle for the MongoDB architecture. Currently, RAC + Local federation uard + Remote Federation uard has become a common HA architecture in the industry. Switchover and failover are the

Oracle, as the most popular commercial database, provides a series of HA solutions in addition to independent database DBMS, to meet actual O & M system requirements. Among them, RAC + Dataguard is our most common HA policy solution and is also

XXXL transaction log Q: Our products use SQL Server to store data. We will release new product versions from time to time, including upgrade scripts for running databases. As we test our latest upgrade script in a typical test database, the size of

Nowadays, Oracle databases are favored by more and more enterprises for their high reliability, security, and compatibility. Many database administrators are concerned about how to maintain excellent performance for Oracle databases. I suggest you

Based on a good database design, using indexes effectively is the foundation for SQL Server to achieve high performance. SQL Server uses a cost-based optimization model, which queries related tables for each commit, determines whether to use or