Verifying SQLHOSTS

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Verifying SQLHOSTS

Make sure that the SQLHOSTS file is set up properly on each server participating in replication.

Setting up Database Server Groups

Enterprise Replication requires that all database servers participating in replication be members of database server groups. Each server in the enterprise must have a unique identifier; the database server group uniquely identifies a server.

If you are combining Enterprise Replication with HDR, both the primary and secondary HDR servers must be members of the same database server group. For more information, see Managing Enterprise Replication with High-Availability Data Replication.

Typically, a server group includes only one database server. However, if the computer has multiple network protocols or network interface cards, the server group includes all aliases for the database server. Enterprise Replication treats the server group as one object, whether it includes one or several database server names.

All Enterprise Replication commands and options use the name of the database server group of the more familiar database server name (that is, the name specified by the INFORMIXSERVER environment variable) for all references to database servers. The exception is the --connect option, which can use both server name or group name. This manual also refers to a database server group as a server group.

This manual uses the convention that the name of a database server group is g_ followed by the name of a database server that is in the group. This use of g_ is only a convention; g_ is not required syntax.

Database Server Groups on UNIX

On UNIX, a database server group is defined in the sqlhosts file. The following example shows a very simple sqlhosts file for four Enterprise Replication servers, john, paul, george, and ringo and their database server groups. The first line describes the database server group g_john, which includes the database server john, and so on.

dbservername	nettype	hostname	servicename	options
g_john john g_paul paul g_george george g_ringo ringo	group ontlitcp group ontlitcp group ontlitcp group ontlitcp	- sydney.australia.com - melbourne.australia.com - perth.australia.com - brisbane.australia.com	- 10110 - 2939 - 5329 - 10101	i=143 g=g_john i=144 g=g_paul i=145 g=g_george i=146 g=g_ringo

The following table describes the fields in the sqlhosts example above.

dbservername	Database server group name or database server name
nettype	Type of connection (composed of the database server product, interface type, and network protocol)
hostname	The name of the computer where the database server resides
servicename	The service name or port number entry in the services file
options	The g option specifies the name of the group to which the database server belongs. The i option specifies a unique identifier for the database server. Make sure that this identifier is consistent for the database server across all nodes in the enterprise.

Important:

The network connection entry should appear immediately after the database server group definition.

Important:

It is not necessary for the DBSERVERNAME to be set to a network connection; however, at least one of server names listed by the DBSERVERNAME or the DBSERVERALIASES configuration parameters should be set to a network protocol. For information about database server aliases, refer to the IBM Informix Dynamic Server Administrator's Guide.

Important:

Enterprise Replication cannot use shared memory connections even if the replicating servers are on same machine.

For an example of an SQLHOSTS file when combining Enterprise Replication and High-Availability Data Replication, see Managing Enterprise Replication with High-Availability Data Replication.

For more information about database server groups and setting up SQLHOSTS, see the chapter on client/server communications in the IBM Informix Dynamic Server Administrator's Guide.

Database Server Groups on Windows

For information about preparing the SQLHOSTS connectivity information on Windows, see Appendix F. SQLHOSTS Registry Key (Windows).

Important:

It is strongly recommended that you use IBM Informix Server Administrator (ISA), rather than regedt32, to set up the SQLHOSTS registry key and database server group registry key on your Windows system. In addition, ISA allows you to administer your replication system from a web browser.

Hierarchical Routing Topologies and SQLHOSTS

For hierarchical routing (HR) topologies:

Root and nonroot servers must each have complete SQLHOSTS server group information for the entire enterprise.
Each leaf server must have SQLHOSTS connectivity information only for itself and its parent (hub).

Root and nonroot servers contain the complete global catalog; leaf servers do not. For more information, see HR Topology Terminology and Global Catalog.

Network Encryption and SQLHOSTS

Client/server network communication is encrypted by specifying the ENCCSM module with the communications support module (CSM) option in the SQLHOSTS file. However, Enterprise Replication can only be encrypted by setting encryption configuration parameters. The ENCRYPT_CDR configuration parameter must be set to 1 or 2 to allow encryption.

Important:

Enterprise Replication cannot use a connection configured with a CSM.

To combine client/server network encryption with Enterprise Replication encryption, configure two network connections for each database server. The configuration in the SQLHOSTS file would look like the following example.

dbservername	nettype	hostname	servicename	options
g_group1 cdr1 serv1	group ontlitcp ontlitcp	- texpdx texpdx	- mp.cdr1 mp.serv1	i=1 g=g_group1 csm=(ENCCSM)

In this example, cdr1 and serv1 are two connection ports on the same database server. Encrypted client/server communications uses the serv1 port, while encrypted Enterprise Replication uses the cdr1 port.

For more information on encrypting client/server network communications, see the IBM Informix Dynamic Server Administrator's Guide.

For more information on encrypting Enterprise Replication, see Setting Configuration Parameters and Appendix B. Configuration Parameter and Environment Variable Reference.

Using the Connection Security Option (s=6)

If you are using the connection security option, s=6, your SQLHOSTS file must contain a regular connection (without s=6) within the same group. To do this, you can add an alias server definition that includes the server group name. For example:

g_serv1 group - - i=10
serv1 ontlitcp lxsun02 ertest1 g=g_serv1, s=6
a_serv1 ontlitcp lxsun02 ertest10 g=g_serv1

For more information about the connection security option, see the IBM Informix Administrator's Guide.