I am working on a data upgrade for a customer. The existing database is from another partner and has tables and fields that my development license does not give me access to.
The database in in version 2016 and I am upgrading to Business Central.
So, I added some functions to the AdvaniaGIT PowerShell module.
To get the table definition from the tenant database I use
(Get-NAVTableMetaDataXml -DatabaseName <tenantDatabasename> -TableId 289 -Snapshot).OuterXml | Out-File C:\AdvaniaGIT\Workspace\xml.xml
The resulting Xml file I can view in any Xml viewer.

This data will help me update my upgrade tables for the Sync-NAVTenant command to complete successfully.
But, I wanted more. Since the destination for the data is in an App table I feel that i have no need for the data in the database during the C/AL upgrade.
I also created the Get-NAVTenanttableNos function that will give me a list of all tables in the tenant database. Using this data I was able to iterate through all the tables and export the structure and data.
I created an empty folder and executed
Get-NAVUpgradeTablesData -TenantDatabase <tenantDatabasename> -ApplicationDatabase 2018-App -CompanyName "MyCompany" -Verbose -ExportPath 'C:\AdvaniaGIT\Workspace\MyCompany'
This gives me all the data that does not fit in the standard 2018-App in separate Xml files .

Each file contains only the fields required to import the custom data. As an example, the xml file for table 17, G/L Entry, does not contain all the data from G/L Entries, just the primary key and the custom fields.
In the Xml file I include details for the table and for the fields included in the data set.
Custom tables that do not have any match in the 2018-App database are exported with all fields. With all the custom data stored safely I can execute the Sync-NAVTenant with Force to get the database upgraded.

The next task is in AL, writing the code to import the Xml files to the App tables.
I will be back with the results from that task…
Hello Gunnar,
What size database did you have and how long did the export data take?
The tenant database is only 11564.69 MB. The export was a little under 4 minutes.