Status files are used to record the operating status of each system service comprising OpenTP1, the status of files, system control information for various devices, etc.

OpenTP1 manages status files for both systems A and B in the following statuses:

• Current
  Status file is open and is subject to output of system control information. A file entity is required.
  
• Standby
  Status file is not currently subject to output of system control information, but it is open so that the current status file can be switched to this status file if the current status file becomes unavailable due to an I/O error, etc. A file entity is required.
  
• Invalid
  Status file has been specified in the status service definition, but it is currently closed and cannot be used in the online mode until it is opened. When all data has been deleted from a file so that it is empty, the file is called an entity-less invalid file. OpenTP1 cannot be started if an entity-less invalid file exists.
  
• Shutdown
  Status file is currently shut down because an error occurred in the status file in the online mode. A status file on shutdown status can be restored to standby status by deleting its file entity with the stsrm command, initializing it with the stsinit command, and then opening it with the stsopen command.
  

The following figure shows the status changes of a status file in the online mode.

Figure 4-2 Status changes for status file in online mode

A maximum of seven status files can be specified in the status service definition for each of the systems (A and B). When OpenTP1 is started normally, the first status file specified in the status service definition is placed on current status, any remaining status files that can be opened are placed on standby status, and any status files that cannot be opened are placed on reserve status. A status file that cannot be opened due to an error is placed on shutdown status. When OpenTP1 is restarted, the previous current file is inherited.

The same information is written in the current status files for both systems A and B.

If an I/O error occurs in one of the current status files for either system A or B, OpenTP1 copies the contents of the other system's current file into a standby file of the systems A and B and then places the standby file on current status. Such switching of current files is called swapping. Files can also be swapped by the user with the stsswap command.

A status file swapped due to an error becomes a spare file if it is deleted by the stsrm command, initialized by the stsinit command, and then opened by the stsopen command.

Where no standby file is available, the processing continues under the normal system alone if one-system operation has been specified in the status service definition (sts_single_operation_switch=continue); OpenTP1 terminates abnormally if one-system operation has not been specified (sts_single_operation_switch=stop).

If, during one-system operation, the normal system fails or OpenTP1 terminates abnormally when a status file is updated, it becomes impossible to restart OpenTP1. Therefore, it is required that double-system operation (both A and B being active) be restored as early as possible by taking either of the following two procedures:

• Open a reserved file with the stsopen command for use as a standby file. Execute the stsswap command to swap the current file.
• Execute the stsrm command to delete the file that has been shut down because of an error. Then initialize the file with the stsinit command and open it with the stsopen command. For one-system operation, if the stsopen command is executed, the contents of the file for the normal system are copied onto the file for the defective system so that it can be reused as a current file.