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…Data Pump Features


Notes:

Datapump exports always estimate the space required for a dump file. The log will contain messages like:
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. estimated "DAVE"."WEBHITS_DETAIL" 39 MB
. estimated "DAVE"."SALES_PER_DAY" 0 KB
Total estimation using BLOCKS method: 43.06 MB
There are two methods available for estimating the space: BLOCKS and STATISTICS. Blocks simply multiples “the number of database blocks used by the target objects times the appropriate block sizes.” Statistics uses the object’s statistics; you’ll want to be sure you recently updated statistics with DBMS_STATS package.
You can ask datapump to provide the estimate and skip the export. This is done with the ESTIMATE_ONLY=Y parameter. You will need to remove or comment out the DUMPFILE parameter if you use ESTIMATE_ONLY=Y.
Though not well documented, the Oracle10g Utilities guide does include this statement: “Use the new Data Pump Export and Import utilities to enable compression during import.” (Original import does not use direct path method – it uses INSERT – and thus imported data is not in compressed format.)