Which servers do you need to enable oracle database?

The necessary components to start an Oracle database instance include: operating system kernel, Oracle database listener, Oracle database instance process and related background processes. The methods for starting these components include: starting a listener (for example: lsnrctl start), connecting to a database (for example: sqlplus / as sysdba), and starting a database instance (for example: startup). Frequently asked questions include failing to start a listener or instance, and debugging methods include checking configuration files or database log files. Optimization recommendations include allocating adequate resources, adjusting parameters, and regular backups.

Oracle Database Server: Those daemons you must enable

The goal of this article is to help you figure out which server-side components are required to start an Oracle database instance and why they are needed. After reading, you will be able to configure a stable Oracle environment with confidence and quickly troubleshoot startup problems. Don't expect me to teach you every step step. This article focuses more on understanding than simple operating guides.

Oracle database is not a single program, it consists of many interdependent processes. To make it run, a series of server-side components need to work together. These components usually run in the operating system background in the form of a daemon process, silently supporting the operation of the database. If you only start the database instance but ignore these heroes behind the scenes, the database may only be paralyzed in front of you.

Basic knowledge: A brief description of Oracle architecture

Don't rush to do it first, we have to talk about Oracle's architecture first. Oracle database instances are composed of multiple processes that jointly manage the database's data and resources. Key processes include:

• Oracle Database Instance Process (ORACLE) : This is the core, responsible for handling SQL statements, managing transactions, etc. Without it, everything is free.
• Listener : The "doorman" of the database, responsible for listening to client connection requests and forwarding the request to the corresponding database instance. If you want to connect to the database, it must be in.

• Background Processes : This is not a process, but a set of processes, for example:

  • PMON (Process Monitor) : Monitors the database process and terminates abnormally. It is like an emergency doctor in the database, always ready.
  • DBWR (Database Writer) : Responsible for writing data from the database buffer to disk. Data persistence depends entirely on it.
  • LGWR (Log Writer) : Responsible for writing redo logs to disk. This is the key to database recovery and cannot be ignored.
  • There are many other background processes, each with its own division of labor, so I won't list them here.

Core concept: The necessary conditions for starting an Oracle instance

To start an Oracle DB instance, you need to make sure that the following components are running:

• Operating system kernel : This is the foundation in the basics. Oracle database runs on the operating system. Without it, everything is empty talk.
• Oracle Database Listener : As mentioned earlier, it is the entry to the client connection. Before starting the database instance, be sure to make sure the listener is started and listened normally.
• Oracle Database Instance Process : This is the core process, responsible for the operation of the database instance.
• Related background processes : These processes are the guarantee for the normal operation of the database and are indispensable.

Practical operation: A simple example (Linux environment)

In Linux environment, you can use lsnrctl start to start the listener, use sqlplus / as sysdba to connect to the database, and then use startup command to start the database instance. But this is just the simplest example. In actual operation, you need to adjust according to your specific environment.

The following is a simple script to start Oracle listener and instance (please modify it according to the actual situation):

 <code class="bash">#!/bin/bash # 启动监听器lsnrctl start # 检查监听器状态lsnrctl status # 启动数据库实例(替换成你的SID) sqlplus / as sysdba </code>

FAQs and debugging

• Listener startup failed : Check the listener configuration file listener.ora to make sure the configuration is correct.
• Database instance startup failed : Check the database log file alert_SID.log to find out the cause of the error.
• Permissions Issue : Make sure your user has permission to start the database instance.

Performance optimization and best practices

Database performance optimization is a big topic, here are a few simple points:

• Reasonable resource allocation : Allocate sufficient memory and CPU resources to the Oracle database.
• Database parameter adjustment : Adjust database parameters according to your actual needs, such as PGA_AGGREGATE_TARGET and SGA_TARGET .
• Regular backup : Back up the database regularly to prevent data loss.

Remember, this article is just a throwaway. The configuration and management of Oracle databases is a complex process that requires you to continue to learn and practice. Don’t be afraid of encountering problems. If you actively investigate, you can become an Oracle expert!

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