Differences between startup, startup mount, and startup nomount

Startup, startup mount, and startup nomount are different startup nomount options: (read the initialization parameter file and start the instance) startup nomount option to start the instance, but do not install the database. When the database is started in this mode, the parameter files are read. background processes and memory structures are started, but they are not attached or communicate with the disk structure of the database. When the instance is in this status, the database is not available. Generally, you can create database, create or recreate control file, mount standby database, and modify parameter. Startup mount Option: (open the control file) the startup nount option executes all the work of the startup nomount option, but attaches the database structure and interacts with the structure. In this case, Oracle obtains information from the control file used to find and attach the data to the main database structure. In this mode, you can execute some management tasks, such as recovery. Reading control file usually starts here for recover dtabase; backup database; rename db files, change archivelog mode and other startup open options: (open data files and log files) if no mode is specified on the STARTUP command line, the startup open option is the default start mode. The startup open option executes all the steps of the startup nomount and startup mount options. This option makes the database available to all users. Open datafile, online redo log startup force option: If you encounter difficulties when starting the database in normal mode, you can use the startup force option. The startup force option first closes the database abnormally and then restarts it. Startup restrict option: the startup restrict option starts the database and places it in OPEN mode, but only gives access to users with restricted session permissions. RMAN> startup nomount connected to the target database (not started) oracle routine started system global region total 135338868 bytes Fixed Size 453492 bytes Variable Size 109051904 bytes Database Buffers 25165824 bytes Redo Buffers 667648 bytes RMAN> startup mount connected to the target Database (not started) oracle routine started Database loaded system global region total 135338868 bytes Fixed Size 453492 bytes Variable Size 109051904 bytes Database Buffers 25165824 bytes Redo Buffers 667648 bytes RMAN> startup connected to target Database (not started) oracle routine started database loaded database opened system global region total 1353 38868-byte Fixed Size 453492-Byte Variable Size 109051904-byte Database Buffers 25165824-byte Redo Buffers 667648-byte there are three types above. startup nomount only starts the instance but does not start the Database, startup mount starts the instance and loads the database, but the database is not open. startup is the most complete. The instance, Database loading, and database opening are all completed. For example:

Microsoft Windows XP [version 5.1.2600] (C) Copyright: 1985-2001 Microsoft Corp. c: \ Documents ents and Settings \ Administrator> cd \ C: \> sqlplus/nologSQL * Plus: Release 9.2.0.1.0-Production on Monday September 21 15:21:50 2009 Copyright (c) 1982,200 2, Oracle Corporation. all rights reserved. SQL> connect/@ dwj as sysdba is connected. SQL> startup nomountORA-01081: unable to start an ORACLE that is already running --- Close SQL first> shutdown abortORACLE routine is disabled. SQL> startup nomountORACLE routine has been started. Total System Global Area 135338868 bytesFixed Size 453492 bytesVariable Size 109051904 bytesDatabase Buffers 25165824 bytesRedo Buffers 667648 bytesSQL>

 

There are several shutdown methods. Which of the following are some disadvantages of shutdown abort? 1. Shut down the database normally. 2. shutdown immediate to immediately shut down the database. Run shutdown immediate in SVRMGRL. The database is not closed immediately. Instead, it is closed after Oracle executes some cleanup tasks (terminate sessions and release session resources). When shutdown is used, the database cannot be closed, shutdown immediate can be used to close a database. 3. shutdown abort closes the database directly, and the session accessing the database is suddenly terminated. If a large number of operations are being performed in the database, after the shutdown abort is executed, it takes a long time to restart the database ---------------------------------------------------- when the shutdown abort process is the same as that of the kill process, the database is immediately closed, and the file status may be inconsistent at this time because the database, make the file time point consistent during the restart and do not need to perform crash recovery. If the checkpoint information is consistent, perform crash recovery. If the checkpoint information is inconsistent (the file header is updated exactly) it is necessary to solve the problem of restoring the media. The most feared problem is that the system has a large number of IO at this time. As a result, writing is suddenly interrupted, and the logical Bad blocks of file blocks happen, the trouble is relatively high, especially when the block of the system tablespace is damaged. Although the probability of shutdown abort error is very small, 1 Only one person may have met one person, but we should be careful. The correct process is shutdown immediate. If the database cannot be down for a long time, observe the IO status on the OS. When there is almost no io, open another shutdown abort window, and there will be almost no problems.