In order to go to NOMOUNT state, oracle scans the content of the pfile/spfile and starts the instance. In the NOMOUNT state :
1.scans pfile/spfile.
2.allocates SGA.
3.starts Mandatory Background processes.
4.creates alert<SID>.log
In the MOUNT state, oracle scans the content of the control file for the physical locations of the data files and Redo Log files. Oracle will not check for the physical existance of these files.
From MOUNT to OPEN, oracle checks for the existance of data files & Redo Log files & it also performs "sanitory check".
Sanitory check is nothing but checking for the synchronisation of SCN(System Change Number).
In order to create a database , we have to be in the NOMOUNT state.
