Extracting a Consistent Database Snapshot
By default, when you export or copy database contents, content is extracted from the source database at multiple points in time. You get whatever is in the database when mlcp accesses a given document. If the database contents are changing while the job runs, the results are not deterministic relative to the starting time of the job. For example, if a new document is inserted into the database while an export job is running, it might or might not be included in the export.
If you require a consistent snapshot of the database contents during an export or copy, use the -snapshot option to force all documents to be read from the database at a consistent point in time. The submission time of the job is used as the timestamp. Any changes to the database occurring after this time are not reflected in the output.
If a merge occurs while exporting or copying a consistent snapshot, and the merge eliminates a fragment that is subsequently accessed by the mlcp job, you may get an XDMP-OLDSTAMP error. If this occurs, the documents included in the same batch or task may not be included in the export/copy result. If the source database is on MarkLogic Server 7 or later, you may be able to work around this problem by setting the merge timestamp to retain fragments for a time period longer than the expected running time of the job; for details, see Understanding and Controlling Database Merges in Administrating MarkLogic Server.