How to migrate only orders with Data Migration Tool?

For orders, you will usually need customers as well.

I used answer when I first did this.

Only run the bin/magento migrate:data command. And with -r if you want to start from scratch.

In your config.xml, comment out the Eav and other steps you want to exclude:

<steps mode="data">
        <step title="Data Integrity Step">
            <integrity>Migration\Step\DataIntegrity\Integrity</integrity>
        </step>
        <!--<step title="EAV Step">
            <integrity>Migration\Step\Eav\Integrity</integrity>
            <data>Migration\Step\Eav\Data</data>
            <volume>Migration\Step\Eav\Volume</volume>
        </step>-->
        <step title="Customer Attributes Step">
            <integrity>Migration\Step\Customer\Integrity</integrity>
            <data>Migration\Step\Customer\Data</data>
            <volume>Migration\Step\Customer\Volume</volume>
        </step>
        <step title="Map Step">
            <integrity>Migration\Step\Map\Integrity</integrity>
            <data>Migration\Step\Map\Data</data>
            <volume>Migration\Step\Map\Volume</volume>
        </step>
        <!--<step title="Url Rewrite Step">
            <integrity>Migration\Step\UrlRewrite\Version191to2000</integrity>
            <data>Migration\Step\UrlRewrite\Version191to2000</data>
            <volume>Migration\Step\UrlRewrite\Version191to2000</volume>
        </step>-->
        <step title="Log Step">
            <integrity>Migration\Step\Log\Integrity</integrity>
            <data>Migration\Step\Log\Data</data>
            <volume>Migration\Step\Log\Volume</volume>
        </step>
        <step title="Ratings Step">
            <integrity>Migration\Step\Ratings\Integrity</integrity>
            <data>Migration\Step\Ratings\Data</data>
            <volume>Migration\Step\Ratings\Volume</volume>
        </step>
        <!--<step title="ConfigurablePrices step">
            <integrity>Migration\Step\ConfigurablePrices\Integrity</integrity>
            <data>Migration\Step\ConfigurablePrices\Data</data>
            <volume>Migration\Step\ConfigurablePrices\Volume</volume>
        </step>-->
        <step title="OrderGrids Step">
            <integrity>Migration\Step\OrderGrids\Integrity</integrity>
            <data>Migration\Step\OrderGrids\Data</data>
            <volume>Migration\Step\OrderGrids\Volume</volume>
        </step>
        <!--<step title="Tier Price Step">
            <integrity>Migration\Step\TierPrice\Integrity</integrity>
            <data>Migration\Step\TierPrice\Data</data>
            <volume>Migration\Step\TierPrice\Volume</volume>
        </step>-->
        <step title="SalesIncrement Step">
            <integrity>Migration\Step\SalesIncrement\Integrity</integrity>
            <data>Migration\Step\SalesIncrement\Data</data>
            <volume>Migration\Step\SalesIncrement\Volume</volume>
        </step>
        <!--<step title="PostProcessing Step">
            <data>Migration\Step\PostProcessing\Data</data>
        </step>-->
    </steps>

Then in your map.xml ignore most product stuff with:

         <ignore>
             <document>catalog_category*</document>
         </ignore>
         <ignore>
             <document>catalog_compare*</document>
         </ignore>
         <ignore>
             <document>catalog_eav_attribute</document>
         </ignore>
         <ignore>
             <document>cataloginventory_stock*</document>
         </ignore>
         <ignore>
             <document>catalog_product_*</document>
         </ignore>
         <ignore>
             <document>core_*</document>
         </ignore>
         <ignore>
             <document>cms_*</document>
         </ignore>

Apologizes for late reply and this was FINAL solution that worked for me.

Config.xml file:

    <steps mode="data">
     <step title="Customer Attributes Step">
         <integrity>Migration\Step\Customer\Integrity</integrity>
         <data>Migration\Step\Customer\Data</data>
         <volume>Migration\Step\Customer\Volume</volume>
     </step>

    <step title="Map Step">
         <integrity>Migration\Step\Map\Integrity</integrity>
         <data>Migration\Step\Map\Data</data>
         <volume>Migration\Step\Map\Volume</volume>
     </step>
     <step title="OrderGrids Step">
         <integrity>Migration\Step\OrderGrids\Integrity</integrity>
         <data>Migration\Step\OrderGrids\Data</data>
         <volume>Migration\Step\OrderGrids\Volume</volume>
     </step>
     <step title="SalesIncrement Step">
         <integrity>Migration\Step\SalesIncrement\Integrity</integrity>
         <data>Migration\Step\SalesIncrement\Data</data>
         <volume>Migration\Step\SalesIncrement\Volume</volume>
     </step>
</steps>

Only command required:

php bin/magento migrate:data vendor/magento/data-migration-tool/etc/ce-to-ce/1.9.2.1/config.xml

Map.xml: Ignore most tables that were creating issue.

User can get such issues in migration like:

[PDOException] SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '77-10' for key 'CAT_PRD_ENTT_MDA_GLR_VAL_TO_ENTT_VAL_ID_ENTT_ID'

Empty these tables to fix issues. You can figure out tables name like this (Note the initials):

'CAT_PRD_ENTT_MDA_GLR_VAL_TO_ENTT_VAL_ID_ENTT_ID' = catalog_product_entity_media_gallery_value_to_entity