I recently came across an issue while exporting a huge partitioned table for a data migration. The export took years without any obvious reason.
After some research I found that the parallelism wasn’t working, I could only see one datapump worker at a time, then I found this note explaining the behaviour (Doc ID 1467662.1) .
A table with BASICFILE lobs cannot be exported in parallel, oracle advise to convert those BASICFILES to SECUREFILES; this was not possible for me.
The second solution was to run multiple export jobs in parallel, each one exporting a fraction of the table rows. In the example, oracle use a query using a range of the primary key to do an export, this was ok but I needed a more automatic method to divide the rows based on the degree of parallelism I wanted to apply, then I found this blog post from Morten Jensen.
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