chmp Command

Purpose

Changes the characteristics of a mirror pool.

Syntax

chmp -A [ -c aiocachelvname ] [ -h highwatermark ] -m mirrorpoolname vgname

chmp -h highwatermark -m mirrorpoolname vgname

chmp -S [-f ] -m mirrorpoolname vgname

Description

The chmp command can perform the following operations:

Configure a mirror pool for asynchronous mirroring using the -A flag.
Set the high watermark of the I/O-cache logical volume with the -h flag.
Detect a change in size of the I/O-cache logical volume and take appropriate actions.
Change the mirror pool from asynchronous mirroring to synchronous mirroring with the -S flag.
Change the I/O-cache logical volume that is used for asynchronous mirroring.

Note:

All disks in all mirror pools must be accessible to be configured for asynchronous mirroring.
After a mirror pool is configured for asynchronous mirroring, some active disks are needed from each mirror pool to convert the mirror pool from asynchronous mirroring to synchronous mirroring. If you want to remove one or more mirror pools from a site that is down, disable asynchronous mirroring using the chmp command with the -S and -f flags.
Asynchronous mirroring is only supported on nonconcurrent scalable volume groups with mirror pools set to be super strict.
You must disable the auto-on and bad-block relocation options of the volume group.
The volume group cannot be a snapshot volume group. The volume group cannot contain active paging-space logical volumes.
The volume group must be varied on to make mirror pool changes.

Flags

Item	Description
-A	Configures a mirror pool for asynchronous mirroring.
-c aiocachelvname	Specifies the name of an asynchronous I/O-cache logical volume. The logical volume must be of the aio_cache type and must not reside in the mirror pool that is specified with the -m flag. If you do not specify the -c flag, the chmp command attempts to find the appropriate logical volume of the aio_cache type.
-f	Forces a mirror pool from asynchronous mirroring to synchronous mirroring, even if the remote I/O cache is not accessible.
-h highwatermark	Specifies the I/O-cache high watermark. The value is the percent of I/O cache size. The default value is 100%. The flag also detects an increase in size of the I/O-cache logical volumes and takes the appropriate action.
-m mirrorpoolname	Specifies the mirror pool name.
-S	Changes a mirror pool from asynchronous mirroring to synchronous mirroring.

Parameters

Item	Description
vgname	Specifies the volume group name where the mirror pool resides.

Examples

To set up an asynchronous mirroring for the mirror pool, enter the following sequence of commands:
1. Create a scalable volume group with the mirror pool set to be super strict on local disks hdisk1, hdisk2, and hdisk3:
```
mkvg -f -S -M s -y gmvg1 hdisk1 hdisk2 hdisk3
```
2. Disable the volume group auto-on and bad-block relocation:
```
chvg -a n -b n gmvg1
```
3. Add the local disks into mirror pool MP1:
```
chpv -p MP1 hdisk1 hdisk2 hdisk3
```
4. Create a logical volume for user data:
```
mklv -b n -p copy1=MP1 -y user_data_lv gmvg1 10
```
5. Add the remote physical-volume devices hdisk4, hdisk5, and hdisk6 to mirror pool MP2 in volume group gmvg1:
```
extendvg -f -p MP2 gmvg1 hdisk4 hdisk5 hdisk6
```
6. Add the remote mirror copy in the volume group using the mirrorvg command:
```
mirrorvg -c 2 -p copy2=MP2 gmvg1
```
7. Add a logical volume of the aio_cache type in the local mirror pool:
  Note: A mirror pool can contain only one I/O-cache logical volume. If the I/O-cache logical volume is mirrored, each copy must be in a local mirror pool.
```
mklv -t aio_cache -p copy1=MP1 -y mp1_aiolv gmvg1 1
```
8. Set up asynchronous mirroring for mirror pool MP2:
```
chmp -A -c mp1_aiolv  -h 80 -m MP2 gmvg1
```
To change the mirror pool from asynchronous mirroring to synchronous mirroring, enter the following command:
```
chmp -S -m MP2 gmvg1
```
To change the mirroring attributes, such as high watermark, enter the following command:
```
chmp -h 90 -m MP2 gmvg
```
To replace the I/O-cache logical volume with a different I/O-cache logical volume, enter the following sequence of commands:
1. Change the mirror pool from asynchronous mirroring to synchronous mirroring:
```
chmp -S -m MP2 gmvg1
```
2. Remove the current I/O-cache logical volume mp1_aiolv that resides in mirror pool MP1:
```
rmlv mp1_aiolv
```
3. Create a new I/O-cache logical volume in mirror pool MP1:
```
mklv -t aio_cache -p copy1=MP1 -y mp1_new_aiolv gmvg1 1
```
4. Set up asynchronous mirroring for mirror pool MP2 using the new I/O-cache logical volume:
```
chmp -A -c mp1_new_aiolv -h 90 -m MP2 gmvg1
```