Questions Related to Data Migration Assistant

Nilesh Patel 111 Reputation points

I am get to the DMA tool, I need to ask some basic questions related to this tool :

    1. Where DMA can break or fails ?
  1. Data transfer rate of DMA tool ?
  2. If tables and data are complex, does it affect the migration? Will DMA handle everything and
    recommend how to resolve it ?
  3. Is DMA hosted only on windows or can host on other OS too?
  4. What if DMA fails, how we will restore it?
  5. Is DMA do assessment and migration 100% from source to the target automatically ?
Azure Database Migration service
Azure SQL Database
SQL Server Migration Assistant
SQL Server Migration Assistant
A Microsoft tool designed to automate database migration to SQL Server from Access, DB2, MySQL, Oracle, and SAP ASE.
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Accepted answer
  1. Alberto Morillo 33,421 Reputation points MVP
    1. I have not seen DMA failing to do its job at any point during a migration or assessment
    2. Data transfer may vary based on your Internet speed, if you are migrating from Azure (IaaS) VM to Azure SQL on the same data center you will have faster migrations. In my experience, 350 to 450 GB databases (on-premises) may take 4-6 hours)
    3. DMA takes care of all complexities, dependencies between tables and objects, constraints.
    4. DMA can be installed only on Windows and only the following Windows versions: Windows Server 2016, Windows 10, Windows Server 2012, Windows 7, Windows 8, Windows 8.1. However, DMA can migrate Linux-based installations of SQL Server to Azure SQL.
    5. I have not seen DMA failing, however the source database will not be affected. DMA will not recover from interrupted migrations (let's say due to Internet service issues), you will have to restart migration to an empty Azure SQL Database.
    6. You can automate DMA assessments using PowerShell and Jupyter Notebooks. Below an example. Using the GUI interface of DMA you need to specify if you are doing an assessment or a migration (project). dmaProcessor -processTo SQLServer -serverName 'localhost\dev2017'
      -databaseName DMAReporting -warehouseName DMAWarehouse
      -jsonDirectory 'C:\temp\Results\' -CreateDMAReporting 1
      -CreateDataWarehouse 0;
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  1. siyao 86 Reputation points Microsoft Employee

    Hey @Nilesh Patel ,

    I am from DMA eng team. Thanks for asking questions. You can also send email to and will get faster response.

    for your questions:

    1. If I understand this question correctly, DMA might crash if assessing so many databases in one assessment. Because DMA consumes memory, out of memory issue might happen but it is rare. DMA v5.5 (we will release very soon) will optimize the assessment algorithm when targeting Azure SQL DB or Azure SQL Managed Instance. Same thing happens to migration. So if you migrate the databases with big data, we suggest using DMS. DMA is a lightweight standalone tool. Also we have a new assessment and migration tool named Azure SQL Migration extension (ADS extension including assessment migration), ( It is a extension in ADS(Azure data studio). If you want to migrate to Azure SQL Managed Instance, i suggest to use this tool. It is very easy to use and it has a better performance than DMA.
    2. DMA migrates data in parallel. The default parallel count is 8. If you already install DMA, you can find a Dma.exe.Config file in DMA installation directory. You can edit the parallel count to speed up the migration.
    3. It affects. It is standalone tool, so the machine hardware affects the performance. DMA cannot handle everything. For example, in migration, DMA doesn't support to migrate sequence. In Assessment, DMA can detect most of issues but not all.
    4. Only windows. This is the download page, It has the details.
    5. If DMA is closed or crash, the assessment or migration under running will be canceled and cannot restored.
    6. I guess the answer should be yes.


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  2. CathyJi-MSFT 21,126 Reputation points Microsoft Vendor

    Hi @Nilesh Patel ,

    >Where DMA can break or fails ?

    It works well for me. Suggest you to do a test in your environment. You can post the issue on this forum when you meet an issue during the process.

    > Is DMA hosted only on windows or can host on other OS too?

    DMA is supported on below Operating Systems.

    Windows Server 2016, Windows 10, Windows Server 2012, Windows 7, Windows 8, Windows 8.1 .

    > What if DMA fails, how we will restore it?

    If the data migration process failed, it will effect source databases, don’t worry about that.

    Suggest you starting from below MS documents to use DMA.

    Overview of Data Migration Assistant
    Best practices for running Data Migration Assistant

    Do a test for this, it is a best choice for you.

    If the response is helpful, please click "Accept Answer" and upvote it, as this could help other community members looking for similar thread.

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