While running the offline tar optimization the below error is thrown.
AEM version is 6.4
The OAK version is Oak 1.8.2
java.lang.IllegalStateException: Attempt to read external blob with blobId [75f0fa0c31558a62efc220ec6f24fa575d66adad5de7e7e545de62c8347f2cba#2268993] without specifying Blob Store
Please can you provide the steps to clear this blob id.
Thanks in advance
Thanks for your reply.I have seen that earlier before rasing the request here and is related to migration.
"i am encountering a problem that there is one dummy blob id which is trying to be migrated but throwing an exception.I think, this BLOB id is of DummyBlobStore."
The issue that we are facing is during Tar optimization.When the tar optimization is run the below error is coming.
For past 3 months after the migration the offline TAR optimization was working fine.
But today run we have this issue.
1) Is there any specific reason you are trying to run offline compaction? 6.4 offers tail online compaction everyday and full online compaction once a week, you should leverage those features.
2) What command are you using to the the offline compaction?
 Revision Cleanup
Thanks a lot for your reply.
We run the commands for removing the reference points as per aem documentation.
java -Dtar.memoryMapped=true -Dupdate.limit=10000000 -Dcompress-interval=50000000 -Xmsvalue -Xmxvalue -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=path -jar /proj/cpmd/oak-run-1.8.2.jar compact storepath
The offline tar compact is more effective since this increases the performance. We will try tail tar optimization with full optimization.
Running Offline compaction on AEM 6.4 is not recommended as per the official documentation at 
Online Revision Cleanup is the recommended way of performing revision cleanup. Offline Revision cleanup should be used only on an exceptional basis - for example, before migrating to the new storage format or if you are requested by Adobe Customer Care to do so.
 Revision Cleanup