How does EXPDP estimate the export space estimate,estimate_only
This article is about how EXPDP estimates the derived space estimate,estimate_only. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.
ESTIMATE
Default: blocks
Specify how to calculate the disk space used by each table
ESTIMATE= [BLOCKS | STATISTICS]
1.BLOCKS-calculated by the number and size of blocks?
2.STATISTICS-calculation of statistics per table
Limit
1. If the table is compressed, then the value calculated using ESTIMATE=BLOCKS is not accurate, so ESTIMATE=STATISTICS.? should be used at this time
two。 It is also not accurate when the QUERY,REMAP_DATA parameter is used
? [oracle@lzl ~] $expdp scott/tiger TABLES=emp ESTIMATE=STATISTICS DIRECTORY=lzl_dir DUMPFILE=estimate_stat.dmp
Export: Release 11.2.0.3.0-Production on Wed Jul 12 23:29:44 2017
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0-64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Starting "SCOTT". "SYS_EXPORT_TABLE_01": scott/* TABLES=emp ESTIMATE=STATISTICS DIRECTORY=lzl_dir
Estimate in progress using STATISTICS method...
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. Estimated "SCOTT". "EMP" 8.203 KB-estimated size
Total estimation using STATISTICS method: 8.203 KB
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
. . Exported "SCOTT". "EMP" 8.562 KB 14 rows-actual size
Master table "SCOTT". "SYS_EXPORT_TABLE_01" successfully loaded/unloaded
*
Dump file set for SCOTT.SYS_EXPORT_TABLE_01 is:
/ home/oracle/expdat.dmp
Job "SCOTT". "SYS_EXPORT_TABLE_01" successfully completed at 23:29:49
ESTIMATE_ONLY
Default: no
If ESTIMATE_ONLY=YES, only estimating the space occupied by the export will not do the actual export work. Can be used to estimate the derived space.
Restrictions:
Cannot be used with the QUERY parameter
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