Reverting to the Old Cluster v11

The method used to revert to a previous cluster varies with the options specified when invoking pg_upgrade:

  • If you specified the --check option when invoking pg_upgrade, an upgrade has not been performed, and no modifications have been made to the old cluster; you can re-use the old cluster at any time.
  • If you included the --link option when invoking pg_upgrade, the data files are shared between the old and new cluster after the upgrade completes. If you have started the server that is servicing the new cluster, the new server has written to those shared files and it is unsafe to use the old cluster.
  • If you ran pg_upgrade without the --link specification or have not started the new server, the old cluster is unchanged, except that the .old suffix has been appended to the $PGDATA/global/pg_control and tablespace directories.
  • To reuse the old cluster, delete the tablespace directories created by the new cluster and remove the .old suffix from $PGDATA/global/pg_control and the old cluster tablespace directory names and restart the server that services the old cluster.