Unable to migrate database from remote MSSQL server: Destination server does not have required login

Symptoms

1. Migration of Plesk subscriptions fails:

   PLESK_ERROR: Sync content
   Failed to copy content of database ‘example’
   Migration tools tried to perform operation in 3 attempts: Command execution failed on the local server with non-zero exit code.
   command: “C:Program Files (x86)Pleskadminbindbbackup.exe” –copy -copy-if-logins-exist -with-data -src-server=203.0.113.2 -server-type=mssql -src-server-login=sa -src-server-pwd=***hidden*** -src-database=example -dst-server=203.0.113.3 -dst-server-login=sa -dst-server-pwd=***hidden*** -dst-database=exampledatabase
   exit code: 23
   stdout: Destination server does not have required login.

   OR

   PLESK_ERROR: Failed to copy content of database ‘database’
   Migration tools tried to perform operation in 3 attempts: Panel Migrator failed to connect to RPC Agent running on ‘203.0.113.3’ server.
   RPC Agent is required for communication between current server and ‘203.0.113.3’ server

2. Remote MSSQL server is used on target Plesk. 

Cause

Remote MS SQL server credentials are not specified in migration session configuration.

Resolution

1. Log in to the target Plesk server
2. Browse to Tools & Settings > Migration & Transfer Manager > Start a New Migration
3. In Setup section select Manual and download RPC Agent installation package, then run it
4. Upload the agent to the remote MS SQL server and edit the file
C:plesk_migratorrpc-agentconfig.ini
to contain the following:

   [GLOBAL]
   ...
   copy-mssql-content: native

   Then run
C:panel-migratorpanel-migrator-rpc-agent.exe 

5. On the target Plesk server, edit the file %plesk_dir%varmodulespanel-migratorsessions<timestamp>config.ini to contain the following (the bold fields should be filled in with the actual values of MS SQL server):

   [GLOBAL]
    ...
    # [optional] external-db-servers
    # Comma-separated list of the sections describing external source database servers.
    # It is highly recommended to specify external database servers for remote MSSQL - otherwise there could be issues
    # when copying database content.
    external-db-servers: mssql1
    ...
    [mssql1]
    # This optional section defines settings of external MSSQL database server 'mssql1'.
    # Fill this section's settings and list it in the 'external-db-servers'
    # setting of GLOBAL section to get the MSSQL databases copied from this server with native MSSQL backup.
    # Remove this section otherwise.
    # [mandatory] os
    # Operating system on which external DB server runs. Could either "windows" or "unix"
    os:
    # [mandatory] host
    # The address of this database server, exactly as displayed in Plesk Panel (usually it equals to database server's IP address).
    host:
    # [mandatory] type
    # Type of the database server - either 'pgsql' or 'mssql'
    type: mssql
    # [mandatory] ip
    # An IP v4 address of this database server.
    ip:
    # [mandatory] windows-username
    # User name of the privileged system user on this centralized mail server. Default is 'Administrator'.
    # windows-username: Administrator
    # [mandatory] windows-password
    # Password of the privileged system user on this database server.
    windows-password:

6. Browse to Tools & Settings > Migration & Transfer Manager and start the migration.