The RBAL background process
coordinates the automatic disk group rebalance activity for a disk group. The other background
processes, ORB0 through ORB9, perform the actual rebalance activity in parallel.
Creating Objects Using ASM
Before a database can use an ASM disk group, the group must be created by the ASM instance. In
the following example, a new disk group, KMS25, is created to manage the Unix disk volumes /
dev/hda1, /dev/hda2, /dev/hdb1, /dev/hdc1, and /dev/hdd4:
SQL> create diskgroup kms25 normal redundancy
2 failgroup mir1 disk '/dev/hda1','/dev/hda2',
3 failgroup mir2 disk '/dev/hdb1','/dev/hdc1','/dev/hdd4';
When normal redundancy is specified, at least two failure groups must be specified to provide
two-way mirroring for any datafiles created in the disk group.
In the database instance that is using the disk group, OMF is used in conjunction with ASM
to create the datafiles for the logical database structures. In the following example, we set the
initialization parameter DB_CREATE_FILE_DEST using a disk group so that any tablespaces
created using OMF will automatically be named and placed in the disk group KMS25:
db_create_file_dest = '+kms25'
Chapter 6: Monitoring Space Usage 181
Creating a tablespace in the disk group is straight to the point:
SQL> create tablespace lob_video;
Once an ASM file is created, the automatically generated filenames can be found in V$DATAFILE
and V$LOGFILE, along with manually generated filenames.
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