Oracle Startup Process Analysis

Oracle Startup Process Analysis:
Oracle generally has several statuses: shutdown, nomount, mount, and open. shutdown to nomount: oracle loads the initialization file to the default directory based on the sid in the environment variable, there are two types of Initialization Files: pfile and spfile. The format is initsid. ora and spfilesid. ora, oracle will first load spfilesid at startup. ora. If not found, initsid will be loaded. ora, allocate the corresponding memory space according to the initialization parameter file, create necessary processes, and then the database enters the nomount state. Nomount to mount status: Open the control file according to the path of the -www.2cto.com-control File Read in the initialization parameter, then reads the control files to get the name of the database datafiles and redo controls, at this point, the databases is still closed and is accessible only to the database administrator. the database admin can keep the database closed while completing speclific maintenance operations, However the database is not available for nomal operations. mount to open status: when open the database, oracle database opens the online datafiles and redo log files. author HeLinHang