Auto failback

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Security Verify Directory provides an option to enable and disable auto failback.

When auto failback is enabled, the proxy server uses the server as soon as it becomes available. However, when auto failback is disabled, servers must be restored by using the resume role extended operation, except in the following cases where auto failback is always enabled:

Cases that always start auto failback and the action taken:
  • All back-end servers go down in a partition.
    Action taken:
    • If a read server is the first server to come back online, the proxy server auto restores that server. Since read servers cannot handle write operations, the first write server that is online is also restored.
    • If a write server is the first server to come back online the proxy server auto restores that write server. Since write servers can handle both read and write requests, no additional servers are automatically restored.
  • All Writeable Backend Servers go down in a partition.
    Action Taken:
    • The first write server to come back online is auto restored by the proxy server.
Note:
  • Auto failback can be enabled or disabled by setting the value of the attribute ibm-slapdEnableAutoFailBack to true or false.
  • The default value of ibm-slapdEnableAutoFailBack is true.

Security Verify Directory also provides you with an option to enable failback that is based on a configurable replication queue size. This feature enables failback to be done automatically only when the replication queue size from the current write server to the server that is being failed back is less than or equal to the configured replication queue size.

To enable failback that is based on a configurable replication queue size by using web administration tool, see Dividing the data into partitions

To enable failback that is based on a configurable replication queue size by using the command line:
  • Set the value of ibm-slapdProxyFailbackBasedOnQueueEnabled attribute to TRUE by running the following command: 
    ldapmodify -D <admin DN of proxy server> -w <admin PW of proxy server> \
-p <port of proxy server> -i modify.ldif

where modify.ldif contains
dn: <RDN of Backend Split Container>, cn=ProxyDB, cn=Proxy Backends, 
cn=IBM Directory, cn=Schemas, cn=Configuration
changetype: modify
replace: ibm-slapdProxyFailbackBasedOnQueueEnabled
ibm-slapdProxyFailbackBasedOnQueueEnabled : <value to be set as either TRUE or FALSE>
  • Set the value of the ibm-slapdProxyFailbackQueueThresholdattribute to a required value by running the following command: 
    ldapmodify -D <admin DN of proxy server> -w <admin PW of proxy server> \
-p <port of proxy server> -i modify.ldif

where modify.ldif contains
dn: <RDN of Backend Split Container>, cn=ProxyDB, cn=Proxy Backends, 
cn=IBM Directory, cn=Schemas, cn=Configuration
changetype: modify
replace: ibm-slapdProxyFailbackQueueThreshold 
ibm-slapdProxyFailbackQueueThreshold : <value to be set in numerals>