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Virtualization with PowerVM > The Hardware Management Console > Data Replication between HMCs

Enable Warnings when manually changing replicated Data

Changes to replicated data should only ever be made on one master. Data is only updated from the master towards the slave(s). If data on a slave is changed manually, the data on the master and slave(s) are no longer synchronous. This is reflected in the following status on the master:

$ hmc lsdatarep hmc01
DATA_TYPE  LEVEL  UPDATED_SINCE_START  UPDATED_TIME         SOURCE_HMC_NAME  NOT_IN_SYNC_SLAVES
pwdpolicy  0      0                    -                    -                -
user       8      1                    05/22/2023 11:58:21  hmc01            hmc03
kerberos   0      0                    -                    -                -
customer   0      0                    -                    -                -
outbound   0      0                    -                    -                -
ldap       0      0                    -                    -                -
mfa        0      0                    -                    -                -
$

For the user data type, the HMC with the name hmc03 is specified in the NOT_IN_SYNC_SLAVES column. This can also be seen on the slave using the status output:

$ hmc lsdatarep hmc03
DATA_TYPE  LEVEL  UPDATED_SINCE_START  UPDATED_TIME         SOURCE_HMC_NAME  NOT_IN_SYNC_SLAVES
pwdpolicy  0      0                    -                    -                -
user       10     1                    05/22/2023 14:06:54  hmc03            -
kerberos   0      0                    -                    -                -
customer   0      0                    -                    -                -
outbound   0      0                    -                    -                -
ldap       0      0                    -                    -                -
mfa        0      0                    -                    -                -
$

The SOURCE_HMC_NAME column should display the name of the master (hmc01). However, the name of the slave HMC (hmc03) itself is displayed. This means the data was last modified on the HMC hmc03 and is no longer synchronous with the master HMC (hmc01).

To ensure that modifications to replicated data on a slave do not go unnoticed, it is possible to configure warnings. For this purpose, the command “hmc chdatarep” can be used on the slave (hmc03):

$ hmc chdatarep hmc03 warning_data_types=user
$

Note: The warning_data_types attribute can also be set when enabling data replication with “hmc enabledatarep“.

If a user account on the HMC hmc03 (slave regarding user) is changed via the HMC GUI, the user is warned:

Customizable Data Replication Warning
Warnung in der HMC GUI beim Ändern eines Benutzer-Accounts der von einer Master HMC repliziert wird.

The administrator then has 3 options to continue:

    • Undo the change (default)
    • Unconfigure all sources (masters) for the data type
    • Ignoring the warning

Note: Unfortunately, this only applies to the GUI and not to the command line!

The data types for which warnings are displayed on the HMC GUI can be viewed with “hmc lsdatarep -l”:

$ hmc lsdatarep -l hmc03
IS_ENABLED  CURR_WARNING_DATA_TYPES  AVAIL_WARNING_DATA_TYPES
1           user                     pwdpolicy,user,kerberos,customer,outbound,ldap,mfa
$