Log-based replication procedure

Site replication with OpenEdge databases is implemented through the use of after-imaging and database backup procedures. For complete information about these procedures, see After-imaging and Back Up a Database.

To implement log-based site replications:

  1. Add after-imaging extents and then enable after-imaging in the primary database. For information about after-imaging extents and enabling after imaging, see After-imaging.
  2. Use the PROSTRCT utility with the LIST option to create a structure description file containing the central database's data structure. For information about the structure description file and the PROSTRCT utility, see Maintain Database Structure.
  3. With the structure description file produced from the central database, use PROSTRCT with the CREATE option to create an additional database on the remote system.
  4. Perform a backup of the primary database to initialize the secondary database. This step creates a basis for subsequent roll-forward operations. For information about performing a backup, see Back Up a Database.
  5. Restore the backup copy of the primary database to the secondary database.
  6. Use the RFUTIL command with the option EXTENT FULL to monitor the after-image extents. This will automatically determine which image extent is ready for replication (or transfer) to the secondary site. You can transfer the after-image extent file to the secondary site using an OS command to remote copy.

    For more information about RFUTIL, see RFUTIL Utility.

  7. Once the after-image extent has been transferred to the secondary site, use RFUTIL with the EMPTY option to mark the extent "empty" and ready for use on the primary database.
  8. Implement a process to monitor and transfer full after-image extents (AI extents). You can copy AI extents to an AI log, then transfer the log contents to the secondary site on a continuous basis.
  9. If it becomes necessary to shift operations to the secondary site, transfer the last "full" and "busy" after-image extents and roll-forward to completion. Start up of the secondary site database causes the database to undergo crash recovery, resulting in the shift to the secondary site.

    For more information about performing roll-forward recovery, see Recover a Database.

The following figure shows after-image extent files replicated from the primary to a secondary database.

Figure 1. Example of site replication