I installed oracle server 12c. In the instalation I created the 'default' instance 'orcl.xxxxxxx.local'. after that I created a table space and after that I created an user and give some grants. I logged to me table space and it worked fine.
but now I want to create a new instance. I'm a little confused about whats is really a instance in Oracle. how can I create a new instance? anyway, I'm using SQL*PLUS to do all that.
thanks.
an Oracle database is a set of files, including: control file(s) datafiles tempfiles redo log files
an Oracle instance is the set of processes accessing the Oracle database.
I suggest you to create the new database instance using dbca in interactive mode, it is simpler than using sqlplus and can you help to understand how an Oracle database instance work.
Create the Oracle database using Sqlplus is a more difficult task and require much more skill.
Here you can find a description for the latter and former methods: http://docs.oracle.com/database/121/ADMIN/create.htm#ADMIN12479
Over than this, if you create the new Oracle instance using dbca, you can ask him to generate creation scripts and you chen run theses scripts from sqlplus. You can modify scripts to create as many Oracle database instances as you want.
Regard Giova
Along with Giova's answer, normally an ORACLE_SID corresponds to an instance. In other words ORACLE_SID and instance have 1:1 relationship ie unless you are in RAC environment which I doubt you are.
