Oracle Database Discussions

Hi

Having a few different mis-understandings here about how oracle starts up etc.

I'm using 11g on Centos[RHEL]. I'm more or less a beginner.

I have the default database configured and another one I plan upon using for a recovery catalog.

Default db: SID = learning, global database name = learningdb.franklyn.bignose.ca

New db [made with dbca]: SID = recovery, global database name = recovery

My issue is basically this: I don't understand why Oracle starts up differently when I use startup mount; alter database open - vs - dbstart $ORACLE_HOME

Here is what my /etc/oratab looks like:

learning:/u00/app/oracle/product/11.2.0/dbhome_1:Y
recovery:/u00/app/oracle/product/11.2.0/dbhome_1:Y

My Experiments:

1: Starting up my databases manually.

$> export ORACLE_SID=learning
$> sqlplus / as sysdba;
SQL> startup mount;
SQL> alter database open;
SQL> exit;
$> export ORACLE_SID=recovery
$> sqlplus / as sysdba;
SQL> startup mount;
SQL> alter database open;
SQL> exit;

Then everything works just fine.

2: Using DB Start

$> dbstart $ORACLE_HOME
Processing Database instance "learning": log file /u00/app/oracle/product/11.2.0/dbhome_1/startup.log
Processing Database instance "recovery": log file /u00/app/oracle/product/11.2.0/dbhome_1/startup.log

Great, but when I connect to my first db like this

$> export ORACLE_SID=learning
$> sqlplus / as sysdba;

I'm told that I have connected to an idle instance. And when I try startup mount, I get

$> sqlplus / as sysdba
SQL> startup mount
ORACLE instance started.

Total System Global Area 849530880 bytes
Fixed Size 1339824 bytes
Variable Size 536874576 bytes
Database Buffers 306184192 bytes
Redo Buffers 5132288 bytes
ORA-01102: cannot mount database in EXCLUSIVE mode

This also happens if i change my oracle_sid to recovery and do same with recovery database.

3: Finally, and this is weird...

$> sqlplus sys/PASSWORD@recovery as sysdba
SQL> exit
$> sqlplus sys/PASSWORD@learningDB as sysdba

Both work just fine. normal. no probs.

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So, does that mean when you have multiple databases and you startup using dbstart, you need to explicitly state the database names on the command line versus relying upon the ORACLE_SID environment variable?

Where as if you start them up manually , you do can rely upon the ORACLE_SID alone?

Why is oracle so cranky like this?

Thanks!