Alejandro Vargas' Blog

A couple of times I've removed ASM disks from a diskgroup and found that the rebalance operation will take too long.

This is not a problem when you don't want to disturb online users, the rebalance process only locks for writes 1mb of data at a time, so letting the rebalance to run slowly has no performance impact.

My problem was that I needed to free the disks as fast as possible in order to finish some IO tests within a limited timeframe.

The procedure to change the rebalance power of an ongoing operation is very simple:

alter diskgroup DATADG rebalance power 6;

After that the rebalance operation will restart with the new set rebalance power.

For a complete example check this document:

Changing the rebalance power of an ongoing rebalance operation

To work on the 11g part of the Labs we will start restoring an 11g database we have on a backup.
The backup consist of an incremental level 0 backupset, a controlfile and spfile backup and the archived logs required to recover the database.

The restore is done in 6 steps
· Re-create the ASM metada
· Restore the spfile
· Restore the controlfile
· Restore the datafiles
· Recover the database
· Open resetlogs

This is covered on this file:
Restoring a Lost Database From Backup

On the previous Labs we created ASM disks based on OS Files, before continuing with the next labs we need to clear them.

This is explained on this file:
Cleanup File based ASM Diskgroups

On this Lab we will review the following crash and recovery scenarios, and we will implement some of them:

• · System tablespace loss
• · Recover system tablespace
• · User datafile loss
• · Recover users tablespace
• · Online redo loss
• · Recover from redo loss
• · Controlfile loss
• · Recover from controlfile loss
• · Database loss
• · Recover from total loss

Details on this file
ASM and Rman Crash Restore and Recovery Scenarios

Sometimes it is required having several clones of the same database running on the same server. That was simple to do when the database was based on File System, and is still simple to do with the help of Rman.

But there are very large databases, which are usually cloned using storage tools like bcv, srdf or snapshots that cannot consider Rman as a viable possibility.

For these databases there is the possibility to implement the procedure we will test on this lab.

Note that the rename disk group script has not been made public.
The rename disk group functionality is available on 11g R2 that was made available to the general public on August 2009.

These are the steps required to complete the process:

1. Prepare a set of storage devices with enough space to hold a copy of the diskgroup to be copied
2. Shutdown the source database
3. Make a bit by bit copy of the source database on the target devices
4. Add kfed path to the path of user root
5. Execute the rename diskgroup script
6. Rename ASM disks of the cloned devices
7. Rescan ASM disks
8. Start the ASM instance and mount the new diskgroup
9. Recreate the controlfile and rename the database based on the cloned diskgroup
10.Open the clone with the resetlogs option

Details on this file:
Cloning Disk Group

On this lab we will review various utilities that provide further information for managing ASM.

Checksum Mismatch After Storage Crash, AMDU an 11g tool that can be used with 10g as well, Blockdumps, Asmiostats and asmdebug

Details on this file: ASM Metadata and Other Checkups

On this lab we will share our ASM disks with a second server and we will open the sati12 database on it.

To do that we copied the vm to another location, without including the ASM disks, that are located on a separate folder, this way the second vm is pointing to the same ASM disks as the first one.

Details on file: Storage Consolidation With ASM

On this lab we will review some of the useful set of commands provided by the ASM command line utility.

Some of the asmcmd commands display information, these information is based on v$asm views, other commands actually make changes to the structure like mkdir or rm.

Details on file: ASMCMD Use And Options