2 spfiles - some confusion

At the moment I'm in a big migration project from 9i to 11gR2.
Most of the migrations are done like

• create new DB


• exp/imp


• delete old DB

Even we have templates for all these steps, sometimes something goes wrong.

Today I hit such a something:
As we use Clusters for most of our DBs, cluster_database=TRUE should be set, otherwise it's generating problems. At the Creation of one DB, the 2nd instance did not come up. After some research I found out cluster_database was set to FALSE. No big deal, let's change it:

alter database set cluster_database=TRUE scope=spfile;

But after a srvctl stop instance -d DB_UNIQUE_NAME -i INSTANCE_NAME

srvctl start instance -d DB_UNIQUE_NAME -i INSTANCE_NAME a show parameter cluster_database still gave me FALSE. This confused me!
So I checked $ORACLE_HOME/dbs/initINSTANCE_NAME and there I found spfile=+ASM_DG/DB_UNIQUE_NAME/PARAMETERFILE/spfile.268.745343891 +ASM_DG/DB_UNIQUE_NAME/PARAMETERFILE/spfile.269.745406153 there where 2 spfiles in the pfile-definition!
After a

create pfile='/tmp/pfile1' from spfile='+ASM_DG/DB_UNIQUE_NAME/PARAMETERFILE/spfile.268.745343891';
create pfile='/tmp/pfile2' from spfile='+ASM_DG/DB_UNIQUE_NAME/PARAMETERFILE/spfile.269.745406153';

and a diff /tmp/pfile1 /tmp/pfile2 I decided to use only the 1st spfile in the $ORACLE_HOME/dbs/initINSTANCE_NAME and apply all the differences manually.
Now both instances are up and fine - I just have to delete the correct spfile in ASM.