I'm exporting one specific table for a schema which I thought was a relatively small 5.4 GB

SQL>  select bytes/1024/1024 MB from user_segments where segment_name='TABLENAME';

However, EXPDP estimates the export size to be over 8 times that size at 46 GB:

Connected to: Oracle Database 12c Enterprise Edition Release - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
Starting "SCHEMA"."SYS_EXPORT_TABLE_01":  SCHEMA/********@DATABASE dumpfile=TABLENAME_20211028.dmp tables=TABLENAME
Estimate in progress using BLOCKS method...
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 45.87 GB

Why is the estimate so much larger than the "table size"?

  • Please provide the expdp sql which you triggered.
    – sarat
    Oct 28, 2021 at 14:24

1 Answer 1


Because the table may have LOB segments that have different names.

select column_name, segment_name from user_lobs where table_name = 'TABLENAME';

And you should check the size of those segments as well.

  • Got it, thank you
    – Huskie69
    Oct 29, 2021 at 13:42

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