Default: BLOCKS
Purpose
Specifies the method that Export will use to estimate how much disk space each table in the export job will consume (in bytes). The estimate is printed in the log file and displayed on the client's standard output device. The estimate is for table row data only; it does not include metadata.
Syntax and Description
ESTIMATE=[BLOCKS | STATISTICS]
BLOCKS
- The estimate is calculated by multiplying the number of database blocks used by the source objects, times the appropriate block sizes.
STATISTICS
- The estimate is calculated using statistics for each table. For this method to be as accurate as possible, all tables should have been analyzed recently. (Table analysis can be done with either the SQL ANALYZE
statement or the DBMS_STATS
PL/SQL package.)
Restrictions
If the Data Pump export job involves compressed tables, then the default size estimation given for the compressed table is inaccurate when ESTIMATE=BLOCKS
is used. This is because the size estimate does not reflect that the data was stored in a compressed form. To get a more accurate size estimate for compressed tables, use ESTIMATE=STATISTICS
.
The estimate may also be inaccurate if either the QUERY
or REMAP_DATA
parameter is used.
Example
The following example shows a use of the ESTIMATE
parameter in which the estimate is calculated using statistics for the employees
table:
> expdp hr TABLES=employees ESTIMATE=STATISTICS DIRECTORY=dpump_dir1 DUMPFILE=estimate_stat.dmp