Off-line Locations

Normally there is a communications link between pairs of locations, and these locations are referred to as on-line. (Their ICONN attribute is 1, and RHOST points to a valid computer name.) However, Global can operate if there is no direct communications link between the Hub and certain locations. These locations are referred to as off-line. (Their ICONN is 0, and RHOST may be unset.)

A tape, CD or other medium is used to copy the databases from one location to the other.

It should be noted that:

• The TRANSFER command copies databases to or from the project directory to a special transfer directory, ready for the physical transfer to another location. The physical transfer must be made as well as using the TRANSFER command from ADMIN.

• The existence of off-line locations limits the administration capabilities of a project.

• Off-line locations can only be children of the Hub. An on-line satellite cannot have off-line children.

• Database transfer to and from the media used for communication with an off-line location can only be made at the Hub and the off-line location.

• Commands such as ALLOCATE and CHANGE PRIMARY are not self-contained. Working practices are required to make sure the correct transfer of data.

Working practices are required to ensure the correct transfer of data. The transfer folder is a holding area for data going to and from the satellite:

• TRANSFER TO offline satellite from HUB copies satellite secondary database to the transfer folder for the satellite (at the Hub)

• The contents of this folder are transferred to the satellite's transfer folder

• TRANSFER FROM HUB at the offline satellite copies satellite secondary databases from the transfer folder at the satellite to the satellite project

• TRANSFER TO HUB at the offline satellite copies satellite's primary databases to the transfer folder for the Hub.

• The contents of this folder are transferred to the hub's transfer folder for the satellite.

• TRANSFER FROM offline satellite at the Hub copies satellite’s primary dbs from the transfer folder at the Hub.

It is potentially unsafe to assume that the system database (apssys) in a transfer folder is the satellite system database. If the TRANSFER FROM step is omitted, then the local system database could be corrupted. This is because the meaning of the file 'apssys' is ambiguous in TRANSFER functionality.

For this reason, the TRANSFER command enforces the use of a location suffix in the Transfer folder. All system databases in the transfer folder always have a location qualifier, including the system database for the Offline satellite and the Project Hub.

Note:
This behaviour is different from that of the GENERATE command, which is used when creating locations.

It is not recommended that users omit the TRANSFER FROM step:

• Potentially, inter-db macro changes could be lost. TRANSFER FROM merges the macros from the transfer folder into the satellite's MISC database, which already might contain local inter-db macros. (Once transferred into the destination project, macros in the transfer folder are renamed with the suffix .macold.)

• If the satellite system database is secondary, then the incoming system db transferred from the Hub will be named with a location suffix. This would need renaming to become the local system db.