Running off from a local disk instead of from a NT share fixed the error reported earlier today. Thanks ninob.
Now there is another interesting requirement which was not clearly stated in any existing E12 documention about mandatory requirement of at least 2 DCs per AD domain.
My test environment has only 1 DC in rootdomain.local and 1 DC in child.rootdomain.local. Does that mean that there is no way to install E12B2 with this setup, including the single DC child domain?
See error below reported in ldif.err:
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Entry DN: CN=ms-Exch-Access-Control-Map,CN=Schema,CN=Configuration,DC=rootdomain,DC=local
changetype: add
Attribute 0) adminDescription:ms-Exch-Access-Control-Map
Attribute 1) adminDisplayName:ms-Exch-Access-Control-Map
Attribute 2) attributeID:1.2.840.113556.1.4.7000.102.64
Attribute 3) attributeSyntax:2.5.5.12
Attribute 4) isMemberOfPartialAttributeSet:FALSE
Attribute 5) isSingleValued:TRUE
Attribute 6) lDAPDisplayName:msExchAccessControlMap
Attribute 7) name:ms-Exch-Access-Control-Map
Attribute 8) oMSyntax:64
Attribute 9) objectCategory:CN=Attribute-Schema,CN=Schema,CN=Configuration,DC=rootdomain,DC=local
Attribute 10) objectClass:attributeSchema
Attribute 11) schemaIdGuid: UNPRINTABLE BINARY(16)
Attribute 12) searchFlags:0
Add error on line 1: Busy
The server side error is "The FSMO role ownership could not be verified because its directory partition has not replicated successfully with atleast one replication partner."
An error has occurred in the program
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Thanks for your help!