(a) Allocate shared disk devices

Specify a character special file to be used for OpenTP1 files. Specify the file to be shared so that both OpenTP1 systems can reference it with the same pathname. Only files created on a character special file can be shared. Contents of ordinary files (e.g., files in the directories $DCDIR/spool/ or $DCDIR/tmp/) cannot be inherited.

(b) Set the IP addresses

In the my_host operand of the system common definition, specify the shared IP address. The same IP address must be specified for both OpenTP1 systems.

(c) Set the HAmonitor environment

Set the HAmonitor definitions. For the HAmonitor environment settings, see the relevant HAmonitor manuals.

In the server statement of HAmonitor, specify the environment for OpenTP1 operations. In the name operand of the server statement, you must specify the full- pathname of the OpenTP1 home directory. For details on other environment settings, see the relevant HAmonitor manuals.

The following definitions of the primary system and the secondary system must match:

• OpenTP1 system definitions
• executable files of a user server (UAP)
• executable files of the transaction service (if you re-create the file with the trnlnkrm command)^#
• versions of program products in the OpenTP1 system
• environment (user ID, group ID, and environment variables) for the OpenTP1 administrator
• absolute pathname of the OpenTP1 home directory
• setting of OpenTP1 files (character special files)
  

  #

  You must also execute the trnlnkrm command to make sure that the order of resource managers registered in OpenTP1 on the primary system is the same as the order on the secondary system.

OpenTP1 does not check for differences in the definitions of two systems, so if definitions do not match, OpenTP1 operation cannot be guaranteed.

(a) Set the system definitions

To use the System Switchover facility:

• Specify Y in ha_conf in the system configuration definition. If this is not specified, a system switch is not possible.
• The specification of the system startup method in the system environment definition (mode_conf operand) differs depending on the reason for starting the standby system, as described below.
  

  When starting the standby system to replace the running system:

  Specify AUTO or MANUAL1.

  If MANUAL2 is specified, an OpenTP1 system which ends abnormally cannot start automatically. To prepare for another system switch, you must use a command to restart the OpenTP1 system.

  When starting the standby system just to complete the postprocessing of the running system:

  To start the standby system just to complete the postprocessing of the running system, such as deciding undecided transactions and ensuring database integrity, specify MANUAL2. This method assumes that, at a minimum, the standby system can perform fall-back operations without any problems. For details about how to have the standby system perform only the postprocessing of the running system, see 6.1.4(1) Starting and terminating OpenTP1.

• To reduce the restart time of the standby system after a system switch, user servers can be specified to be started before OpenTP1 is started. Specify Y in the user_server_ha operand in the system environment definition.

(a) LAN components to be used

When the System Switchover facility is used, the LAN components and communication lines used by OpenTP1 are online in the running system, and offline in the standby system. Whenever the running system switches, the LAN components and communication lines in that system automatically go offline.

If you want to perform maintenance on an offline standby system, you should not use the LAN components and communication lines that are used by OpenTP1. This is because both the running system and the standby system share the same IP address, so there is a possibility of confusion when both systems are performing network-related activities. To perform such maintenance tasks, use a console or prepare a maintenance LAN, one not used in usual system switching.

(b) File system to be used

When using the System Switchover facility, use the OpenTP1 file system. If an ordinary UNIX file system is used, OpenTP1 might not start.

(c) Using mirrored disks

Whether the information on a shared disk device can be duplicated using mirrored disks depends on the operating system and hardware that you use. Use mirrored disks based on the specifications such as those for the mirrored disks and cluster facility of the operating system and hardware.

If a system switchover occurs while writing to two disks using a mirrored disk, inconsistency may occur between the two disks due to a delay in writing. If the written data is not correct in the disk of the system to which the operation should be switched over, OpenTP1 cannot operate normally after a system switchover.

The following OpenTP1 files are essential to operate OpenTP1:

• Status files
• System journal files
• Checkpoint dump files

To use mirrored disks for these OpenTP1 files, make sure that the operating system and hardware allow using mirrored disks for shared disk devices and that the data in the disk devices is correct even when the System Switchover facility is used.

To improve the reliability of files that cannot be written to mirrored disks:

• duplicate the status files and system journal files.
• duplicate the checkpoint dump files or use the multi-generation guarantee facility for checkpoint dump files.