Oracle Database Startup Stages

Oracle Database Startup Stages

 

1.      Startup(Nomount)

2.      Mount

3.      Open

 

when startup command is issue to start the database then database startup goes from these three stages:-

 

1.      Startup(Nomount) :-  this is the first stage of database startup at this stage database entered in nomount stage where parameter file is read (i.e. init.ora). In which all the database parameter are read which includes all the memory areas and parameter like

 

 

user_dump_dest location

background_dump_dest location

core_dump_dest location

db_cache_size

java_pool_size

etc.

if any of the parameter is not correct or any of the file is not available at the location mentioned in parameter file then database doesn't start .

 

2.      Mount :-  this is the second stage of database startup at this stage database control file is read.in which all the datafiles address and database information is read if any file is not at the address mentioned in control file then database doesn't opened and shows error of missing file.

 

3.      Open :-  the last stage of startup is open at this stage all the datafiles are accessed

                        after accessing datafiles ,oracle checks that all the files are consistent or not.