Pre-Stage vs. Big Bang Strategy for Public Folders

The easiest and cleanest migration strategy for Public Folders is the Big Bang strategy. This refers to migrating all of the data in one pass. This is most suitable when migrating when the project is not migrating more than a few GB of data for the whole project.

For larger Public Folders, follow a multi-pass strategy, which is defined below. This refers to migrating data older than a defined date for the first Full pass, and then performing a second Full (Delta) pass.

When following this strategy, you will not be selecting Pre-Stage from the Start drop-down list. For this scenario, you will first be migrating older data (using Date range filtering, which is set under the Advanced Options of the Project) via a Full Migration pass. Then you will perform another Full Migration (Delta) pass, having removed the date filtering​.

It is very important to follow the exact steps, as outlined below. Connectivity problems and timeouts can cause Public Folder migrations to restart, which will increase the time for migration. The strategy, in conjunction with setting the proposed project Advanced Options, will provide optimal migration speeds.

Here are the MigrationWiz steps to perform a Public Folder migration. The Source and Destination environments must be prepared before running through these steps. For details, refer to the migration guide that matches your scenario.

From the MigrationWiz Public Folder main dashboard:
  1. Select the Public Folders that will be migrated.
  2. Click the Start button.
  3. Choose Full Migration from the drop-down list.

For smaller Public Folder migration projects, follow a Big Bang Migration strategy. This will migrate all data at once, rather than performing multiple migration passes. This will take time to complete, but it will avoid the issues indicated above. It is not necessary to add any Advanced Options flags for this type of migration strategy; all that is needed is to select Full Migration from the drop-down list, under the Start button.

For larger Public Folders, (>20 GB) follow a multi-pass strategy:

First pass

Under project Advanced Options:

      • Set the MaintainWatermarkCompletionState flag. It should be added under the Advanced Options/Support/Support Only field in the project: MaintainWatermarkCompletionState=1

      • Set the date to migrate items older than six (6) months. This should be set under Advanced Options/Filtering/Only migrate items whose create date is before a specified​ date. Set the date to be six (6) months prior to the current date, and set the time to be 0/0.

Make a note of this date, because during the Delta pass you will migrate items newer than this date.

    • Select the Public Folders to be migrated, click the Start button, select Full migration, and click the Start Migration button.

Second pass

Under project Advanced Options:

  • Set the SkipImportFolderWhenPublicFolderExists flag, after we know there has been at least one item migrated. It should be added under the Advanced Options/Support/Support Only field in the project: SkipImportFolderWhenPublicFolderExists=1

Why it is important to add this flag? A separate call, in addition to the call for the initial retrieval of the folders, has to be made to retrieve permissions (i.e., cannot include permission in the initial list of properties to retrieve). This means that not only do we need to make a call to the Exchange server to retrieve all the folders at the current point in the hierarchy, but we have to make a separate call per folder to Exchange to retrieve that folder's current permissions. 

Due to the large number of folders, this can significantly increase the initial folder retrieval and migration. However, this can be skipped when running the Delta pass, since retrieval of folders, and permissions, were made during the first pass.

It is skipped by setting the SkipImportFolderWhenPublicFolderExists=1Advanced Option.

If new folders or items are created after the first pass, this flag will not affect the retrieval of the folders and permissions for these, because it only skips existing folders. No new permissions should be added after the Pre-Stage pass, however, since it will skip migrating these if this flag is set.

  • Remove the MaintainWatermarkCompletionState=1 Advanced Option before running the Full (Delta) Migration pass.

Since the flag is removed, MigrationWiz will now run another index before the second pass begins. However, if the date filter is added in the next step, then this will vastly improve the speed of the second pass, since it won't have to re-index ALL Public Folders.

  • Set the date to migrate items newer than six (6) months. This should be set under Advanced Options/Filtering/Only migrate items whose create date is after a specified date.

An example of date filter: If, during the first pass, a date filter is set to migrate only items older than 2/1/2015, at 0 hours, 0 minutes, then before running the Full (Delta) Migration pass, it is necessary to enter a date filter under Advanced Options, to migrate items newer than 2/1/2015 at 0 hours, 0 minutes.

Be sure to remove the date filter set in the first pass, i.e., remove the checkmark from the box labeled Only migrate items whose create date is before a specified date.

By adding this date filter, MigrationWiz needs to index and thus watermark only recent items that were not included in the first migration pass.

If following a multi-pass migration strategy, review the information in the article, How do I Enable Office 365 Users to Access Legacy On-Premises Public Folders? This is important if the migrated users will still access the on-premises Public Folders during migration.

  1. Select the Public Folders to be migrated.
  2. Click the Start button.
  3. Select Full migration.
  4. Click the Start Migration button.

Further information on why it is important to add the flag MaintainWatermarkCompletionState=1 during the first pass:

When there is a large amount of data in Public Folders, there can be a higher number of errors than in mailbox migrations. This could happen for a number of reasons, like corrupt items or incompatible MIME type items within the Public Folders. These errors slow the process down since MigrationWiz will be running many checks to try to migrate the items with errors. Without this flag, MigrationWiz will have to re-index all Source Public Folders again, before the migration can begin.

If a BitTitan server restarts due to Microsoft patching, it will have to begin scanning and indexing all over again before it can begin migrating. The flag will ensure that MigrationWiz can begin from where it left off, upon restart.

We recommend that this should be set before the first migration pass. Remember to remove this prior to performing a second Full (Delta) migration pass, if there is an expectation of any new items to be added to the Public Folders after the first migration pass.

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