Analysis of Oracle Database Service on Windows

If you deploy an Oracle database system on a Windows operating system, the startup process is written to the service list of the operating system. And some major services will be set to auto start. In this case, the database is automatically started when the operating system is started. These services are also automatically disabled when the operating system is disabled. As shown in, it is a typical service of the Oralce Database System under the Windows operating system.

1. understand Major Oracle database services.

Although it lists a lot of Oracle database services, we only use four of them in the actual process. OracleTNSListener (the second service in, which corresponds to the Database Listener), OracleServiceDTM123 (the first service in, corresponds to the data library routine), and oracledbmongoledmt123 (the last service in, corresponding to the Enterprise Manager of the database) and OracleiSQL * Plus (the fifth service in the table corresponds to the Isql * plus tool of the database ). The database administrator must be familiar with the functions and relationships between the four services. The database administrator needs to use this service list to manage the database startup and shutdown.

For example, when starting these database services, it will occupy a large amount of memory, CPU and other system resources. Sometimes installing the Oracle database system on a Windows operating system may only be for testing, training, and other purposes. To this end, it is unnecessary to keep these database services running and affect other services on the operating system. Therefore, sometimes the Database Administrator does not want these database services to be automatically started as the operating system starts. They hope to manually start these services as needed. In this case, these services will not take up valuable routines when no database is needed. In this case, the database administrator needs to change the Startup Mode of these services. As shown in, you can set the preceding four services to "Manual. In this case, the database system will not be automatically started as the operating system starts. To change the Startup Mode of these services, you only need to select the corresponding service and double-click the service to open a service management dialog box. In this dialog box, we can find a drop-down list of startup types. You can change the Startup Mode of these services by selecting "Manual. By default, the start type is "automatic ". If you do not need these services, you can even set the Startup Type to "disabled ".

2. Understand the relationship between various services.

Oracle services have a complex relationship, which is mainly reflected in their strict interdependence. When starting or disabling a service, you must start or close it in a certain order. Otherwise, an error message may appear. For example, for the above four main services, the relationship between them is more complex. Generally, you can only start the OracleTNSListener service. If other database services, such as oracledb1_ledmt123 (Database Enterprise Manager), are enabled without enabling this service, an error occurs. The system will prompt: "Some services depend on the loading sequence of other services, system drivers, or groups. If the system build is stopped or not running properly, services dependent on it will be affected ". Simply put, the Enterprise Manager service cannot be started if the listener service is not enabled. There is a dependency between the two services. Similarly, the Enterprise Manager Service and OracleServiceDTM123 (Data Warehouse routine) service are also closely related. To use the Enterprise Manager Service, you must first start the Data Warehouse routine service. Otherwise, the above exception information will be thrown.

The Database Service is affected by the preceding restrictions when it is started. This is also true when you close these services. However, this is much better than when the service is started. when the service is closed, operations will automatically detect whether there is a dependency service. If it exists, other services will be automatically disabled before the service is closed. For example, the Database Enterprise Manager Service and data warehouse routine service are started simultaneously in the operating system. Now that the database administrator does not need an Oracle database, he needs to disable the Data Warehouse routine service to release memory and CPU resources. When you close the service, the operating system finds that the Service (Enterprise Manager) that is being started needs to use the service that is being closed. In this case, the operating system first closes the Enterprise Manager service and then closes the Data Warehouse routine service. That is to say, when a service is started, if there is dependency between services, the operating system will not start automatically. Instead, an exception message is thrown, allowing the database administrator to manually start the associated service. However, when you close a service, the operating system automatically closes the service if it encounters an interdependent service. Therefore, when shutting down a service, the database administrator must understand the interdependence between them. To disable a service, you must disable other services in use. This may cause unnecessary losses to users.

Iii. Differences between starting a database using services and starting a database using commands.

When using commands to start a database, you can use different options to enable the database to start in different States. For example, commands are usually used to start the database, and different options are used to enable the database to only start the routine (with the Nomount option), mount the database, and not open the database (with the mount option) open the database (using the open option) or open the database system in restricted mode (with the restrict option. Sometimes opening the database system in a specific way is very important for the database administrator to maintain the database. If the database administrator needs to move a database file to a new hard disk to reduce hard disk I/Q conflicts or switch the database from non-archive mode to archive mode, you need to start the database to the Mount mode. That is, open the control file instead of the data file. In this case, you can change the content of the control file (the control file has been opened) or move the data file (the data file has not been opened yet in Mount mode. Only in this mode can data files be renamed and moved. In addition, commands can be used for conversion in different modes. If you are currently in the database Mount mode, you can use the alter database open command to convert the database to the open mode. These functions cannot be completed through the Oracle service.

However, it is impossible to control the startup and shutdown of databases through services. Generally, the database is started only when the listener service, data library routine service, and Database Enterprise Manager Service are enabled at the same time. Or, the database is open only when the Database Enterprise Manager Service is started. The Enterprise Manager service can be started only after the listener service and data warehouse routine service are started. Therefore, when the Enterprise Manager Service is started, the three services are started at the same time. If a service is closed, the database is closed.

It can be seen that there are many differences between commands and services to manage database startup and shutdown. In general, I suggest you maintain the database startup and shutdown operations by using commands. However, services can also provide functions that cannot be implemented by commands. For example, if the database administrator does not want the database to be automatically started with the startup of the operating system, you can change the corresponding Service Startup type. For example, you can set the preceding Service Startup type to "Manual. When the operating system is started, the database system will not be started automatically. However, this is mainly used on some test servers or training servers. For database servers used in enterprise production environments, you must set this service to automatically start. That is, the database service is automatically started when the operating system is started to reduce the workload of the database administrator. Therefore, although database startup and shutdown processes are managed through services, it is an extensive management. But sometimes the Database Administrator does not need it.

In Windows, the database system is automatically started with the startup of the operating system by default. In Linux, when the system platform does not have such a service management mechanism, when the Oracle database system is deployed in the Linux operating system, by default, it will not start with the startup of the operating system. If the database administrator needs to enable automatic startup with the operating system, add related commands to the startup list. This is an obvious difference in deploying Oracle databases on two different operating systems.

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