For an HDR database server pair to function, you must fully configure each of the database servers. For information on configuring a database server, refer to Installing and Configuring the Database Server. You can then use the relevant aspects of that configuration to configure the other database server in the pair. For more information on the configuration parameters, see the IBM Informix Administrator's Reference.
This section describes the following configuration considerations for HDR database server pairs:
The versions of the database server on the primary and secondary database servers must be identical.
The number of dbspaces, the number of chunks, their sizes, their pathnames, and their offsets must be identical on the primary and secondary database servers. In addition, the configuration contain at least one temporary dbspace. See Use of Temporary Dbspaces for Sorting and Temporary Tables.
You should use symbolic links for the chunk pathnames, as explained in Allocating Raw Disk Space on UNIX.
The following ONCONFIG parameters must have the same value on each database server:
The page size of a dbspace and the buffer pool specifications are automatically propagated from the primary to the secondary database server. While both the primary and the secondary database servers must have the same buffer pools, the number of buffers in the buffer pools do not need to match.
You do not have to set the MIRROR parameter to the same value on the two database servers; you can enable mirroring on one database server and disable mirroring on the other. However, if you specify a mirror chunk for the root chunk of the primary database server, you must also specify a mirror chunk for the root chunk on the secondary database server. Therefore, the following ONCONFIG parameters must be set to the same value on both database servers:
The physical log should be identical on both database servers. The following ONCONFIG parameters must have the same value on each database server:
You can specify different tape devices for the primary and secondary database servers.
If you use ON–Bar, set the ON–Bar configuration parameters to the same value on both database servers. For information on the ON–Bar parameters, see the IBM Informix Backup and Restore Guide.
If you use ontape, the tape size and tape block size for the storage-space and logical-log backup devices should be identical. The following ONCONFIG parameters must have the same value on each database server:
To use a tape to its full physical capacity, set LTAPESIZE and TAPESIZE to 0.
All log records are replicated to the secondary server. You must configure the same number of logical-log files and the same logical-log size for both database servers. The following ONCONFIG parameters must have the same value on each database server:
The database server logs the addition of logical-log files. Logical-log files added dynamically on the primary server are automatically replicated on the secondary server. Although the DYNAMIC_LOGS value on the secondary server has no effect, keep DYNAMIC_LOGS in sync with the value on the primary server, in case their roles switch.
The following HDR configuration parameters must be set to the same value on both database servers in the replication pair: