how to set backup restore cache dir in localconfig?

[serivo]

Hi, I have exported by nfs /opt/zimbra/backup from one server to another in order to migrate mail. When I tried restore from backup by web interface, I got the message:
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Error code: service.FAILURE Message: system failure: Unable to create temp file under /opt/zimbra/backup/tmp/restore/shared_blobs; make sure the directory exists and is writable, or set localconfig key backup_restore_cache_dir to a writable location Details:soap:Receiver
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Should I create zimbra writable directori /opt/zimbra/tmp and set it by
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zmlocalconfig -e backup_restore_cache_dir=/opt/zimbra/tmp
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Or it should be something like ZimbraBackupRestoreCacheDir?
I did not find any reference to such keys not in forums, wikies, or in /opt/zimbra/conf files.
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Sergey