Use Multiple Mapping Files at Once

PowerShell allows you to use multiple mapping files for migrating your objects or content.

Follow this example script: 

# Import a Content Type Mapping to a new Mapping Settings
$mappingSettings = Import-ContentTypeMapping -Path "c:\MyMappings\ContentTypeMappings.sgctm"

# Add a Property Mapping
$mappingSettings = Import-PropertyMapping -Path "c:\MyMappings\PropertyMappings.sgpm" -MappingSettings $mappingSettings

# Add a Permission Level Mapping
$mappingSettings = Import-PermissionLevelMapping -Path "c:\MyMappings\PermissionLevelMappings.sgrm" -MappingSettings $mappingSettings

# Add a User And Group Mapping
$mappingSettings = Import-UserAndGroupMapping -Path "C:\MyMappings\UserAndGroupMappings.sgum" -MappingSettings $mappingSettings

# Display the whole mapping settings
$mappingSettings

You can now use the $mappingSettings object in your copy command. The important thing to note is that each cmdlet that generates a mapping settings object has a switch called '-MappingSettings' which allows adding mapping settings to an existing mapping settings object.

$srcSite = Connect-Site -Url "http://myfarm1/sites/mysourcesite"
$dstSite = Connect-Site -Url "http://myfarm2/sites/mydestinationsite"
$result = Copy-Site -Site $srcSite -DestinationSite $dstSite -Merge -MappingSettings $mappingSettings
$result  
Export-Report $result -Path "C:\MyReports\CopySiteReports.xlsx"