Many sites use procedures to enable automatic startup of one or more Oracle Database instances and databases immediately following a system start. The procedures for performing this task are specific to each operating system. For information about automatic startup, see your operating system specific Oracle documentation. If your local Oracle Database server is part of a distributed database, you might want to start a remote instance and database.
Procedures for starting and stopping remote instances vary widely depending on communication protocol and operating system. You can alter the availability of a database. You may want to do this in order to restrict access for maintenance reasons or to make the database read only.
The following sections explain how to alter the availability of a database:. When you need to perform specific administrative operations, the database must be started and mounted to an instance, but closed. You can achieve this scenario by starting the instance and mounting the database.
You can make a mounted but closed database available for general use by opening the database. Opening a database in read-only mode enables you to query an open database while eliminating any potential for online data content changes.
While opening a database in read-only mode guarantees that datafile and redo log files are not written to, it does not restrict database recovery or operations that change the state of the database without generating redo. For example, you can take datafiles offline or bring them online since these operations do not affect data content.
If a query against a database in read-only mode uses temporary tablespace, for example to do disk sorts, then the issuer of the query must have a locally managed tablespace assigned as the default temporary tablespace. Otherwise, the query will fail. Ideally, you open a database in read-only mode when you alternate a standby database between read-only and recovery mode.
Be aware that these are mutually exclusive modes. After placing an instance in restricted mode, you should consider killing all current user sessions before performing any administrative tasks. Control is not returned to the session that initiates a database shutdown until shutdown is complete. Users who attempt connections while a shutdown is in progress receive a message like the following:.
There are several modes for shutting down a database. These are discussed in the following sections:. Some shutdown modes wait for certain events to occur such as transactions completing or users disconnecting before actually bringing down the database. There is a one-hour timeout period for these events.
This timeout behavior is discussed in this additional section:. Before the database is shut down, the database waits for all currently connected users to disconnect from the database. When the database or one of its applications is functioning irregularly and you cannot contact users to ask them to log off or they are unable to log off. No new connections are allowed, nor are new transactions allowed to be started, after the statement is issued. Any uncommitted transactions are rolled back.
If long uncommitted transactions exist, this method of shutdown might not complete quickly, despite its name. Oracle Database does not wait for users currently connected to the database to disconnect. The database implicitly rolls back active transactions and disconnects all connected users. After all transactions have completed, any client still connected to the instance is disconnected.
A transactional shutdown prevents clients from losing work, and at the same time, does not require all users to log off. You can shut down a database instantaneously by aborting the database instance. If possible, perform this type of shutdown only in the following situations:. The database or one of its applications is functioning irregularly and none of the other types of shutdown works.
You need to shut down the database instantaneously for example, if you know a power shutdown is going to occur in one minute. The database implicitly disconnects all connected users.
The next startup of the database will require instance recovery procedures. Shutdown modes that wait for users to disconnect or for transactions to complete have a limit on the amount of time that they wait.
If all events blocking the shutdown do not occur within one hour, the shutdown command cancels with the following message: ORA user requested cancel of current operation. The quiesced state lets administrators perform actions that cannot safely be done otherwise. These actions include:. Actions that fail if concurrent user transactions access the same object--for example, changing the schema of a database table or adding a column to an existing table where a no-wait lock is required. Actions whose undesirable intermediate effect can be seen by concurrent user transactions--for example, a multistep procedure for reorganizing a table when the table is first exported, then dropped, and finally imported.
A concurrent user who attempts to access the table after it was dropped, but before import, would not have an accurate view of the situation. Without the ability to quiesce the database, you would need to shut down the database and reopen it in restricted mode.
Create a free Team What is Teams? Learn more. Asked 7 years, 8 months ago. Active 3 years, 3 months ago. Viewed 19k times. I have a question here about Oracle data guard. At this stage, sometimes I find DBA performance in 2 different steps: startup mount; startup nomount; then alter database mount standby database; What's the difference between above commands?
Could somebody tell me? Thanks for helping me and forgive me about my English writing. Improve this question. DevYudh DevYudh 1 1 gold badge 8 8 silver badges 14 14 bronze badges. Have you read dba-oracle.
Add a comment. Active Oldest Votes. Improve this answer. Alex Poole Alex Poole 2, 1 1 gold badge 16 16 silver badges 22 22 bronze badges. Start up mount:database is mounted i.
Now the database is ready to use. Profile Answers by pattiprashanth. Startup NoMount: when you trigger "startup nomount".
Startup Mount: when you trigger "startup mount". In this stage database is ready to be opened. At first,database is at rest. After startup nomount,Oracle 1st read parameter file,start background processes then allocate memory. Startup nnomount: Oracle will read the initialization parameter file SPfile or PFile to allocate the memory structure SGA and to run the Background processes, this is used to create the database, and to recreate the SPfile and to recreate the Control file. Startup Mount: in this state the Oracle will be already in Nomount state then altered to Mount state, in this state the Controlfiles will be allocated and opened and read as their location is in the initialization parameter file, then oracle will read the control file which containing many critical information like : the location for the datafiles and the online redolog files.
Please Turn OFF your ad blocker.
0コメント