DB2 Version 10.1 for Linux, UNIX, and Windows

hadr_target_list - HADR target list database configuration parameter

This parameter, which enables HADR to run in multiple standby mode, specifies a list of up to three target host:port pairs that act as HADR standby databases.

Configuration type

Database

Applies to

Database server with local and remote clients
Database server with local clients

Parameter type

Configurable online

Default

NULL

For HADR to run in multiple standby mode, you must set the hadr_target_list configuration parameter on all HADR databases. You cannot switch from single standby mode to multiple standby mode by setting this parameter without shutting down the primary. The host:port pairs that you specify for the hadr_target_list configuration parameter for a primary determine which hosts act as standbys for that primary. The host:port pairs in the target list of a standby identify the standby hosts to be used if this standby takes over as the new HADR primary database.

The default setting of NULL, indicates that HADR runs in single standby mode.

As with the hadr_remote_host and hadr_local_host database configuration parameters, the host that you specify for the hadr_target_list configuration parameter can be either a host name or an IP address. A host name can contain alphanumerics, dashes, and underscores only. As with the hadr_remote_svc and hadr_local_svc configuration parameters, the port that you specify for the hadr_target_list configuration parameter can be either a port number or a service name. A service name can consist of any characters. A host name is mapped to an IP address, and a service name is mapped to a port number. The values that you specify for the hadr_target_list configuration parameter can contain a combination of host names, host IP addresses, service names, and port values. Specify the host:port pairs in the following format:

host1:port1|host2:port2|host3:port3

You must enclose Numerical Internet Protocol version 6 (IPv6) addresses in square brackets ([]) to differentiate the IP part from the port part, as in the following example:

[FEDC:BA98:7654:3210:FEDC:BA98:7654:3210]:4000

The first entry in the target list of an HADR database is designated as the principal HADR standby database, and any other entries are called auxiliary HADR standby databases. You can configure the principal standby database and the primary database to use any synchronization mode; however, the synchronization mode of the principal standby is determined by the setting for the hadr_syncmode configuration parameter on the primary. The synchronization mode of the auxiliary standby targets is always SUPERASYNC. When you start HADR on the primary, the values for the hadr_remote_host and hadr_remote_svc configuration parameters are automatically set to those of the principal standby unless you set the DB2_HADR_NO_IP_CHECK registry variable to ON.

There is no requirement for symmetry or reciprocal settings. For example, database A can designate database B as its principal standby, and database B can designate database C as its principal standby. However, role switch between any pair of the databases must be able to occur. For example, if database B is listed in the target list of database A, database A must be listed in the target list of database B.

Although the hadr_target_list parameter can be updated and take effect while the database is online, there are some restrictions if HADR is active:

You cannot change the principal standby of the primary without first stopping HADR on the primary.
You cannot remove a standby from the list if it is connected to the primary. To disconnect a standby, simply deactivate it. Then you can remove it from the primary's target list.
You cannot dynamically update the hadr_target_list configuration parameter for a standby unless you have enabled the HADR reads on standby feature.
You cannot remove the primary database from the target list of a standby if the standby is connected to the primary.
The target list must contain IP address that are either IPv4 or IPv6, but not a combination of the two.