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Thursday, July 14, 2016

Compress/Uncompressed Data During Import in 12c




COMPRESSION options is

COMPRESSION_ALGORITHM=[BASIC | LOW | MEDIUM | HIGH]

BASIC offers the most efficient usage of CPU and effective compression ratio; it is deemed to be applicable to most sessions.
LOW favors size in comparison to CPU and yields a larger file size with a lower compression ratio.
MEDIUM is similar to BASIC. It uses a different algorithm as it performs the work at hand.
HIGH is a good choice when the size of the export file is the determining factor; on the source site, it yields the smallest file, but it could be the most CPU-intensive.
For example

impdp directory=exam_dir dumpfile=ocp.dmp logfile=impdp_ocp.log 
     remap_schema=test:user transform=table_compression_clause:compress

expdp  directory=exam_dir dumpfile=ocp.dmp logfile=expdp_ocp.log
        compression=all compression_algorithm=low

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