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I would be really helpful to see what you have been doing but you have not posted your DML.1 person found this helpful
You can determine compression with DBMS_LOB.GETLENGTH.
If you are not seeing compression then it is likely Oracle has determined that it can not get past the 20% threshhold
under which it will not compress because it believes the overhead is greater than the benefit.
to measure how large a LOB value is when it is uncompressed just copy it to another table actually another LOB segment without LOB compression
and check out dbms_space.space_usage procedure.
This will tell you the thinks you are interested in.
I've used the getlength method but that only tells me the uncompressed size of a record. I don't really need that since I have the original, uncompressed, file to compare things with.
The compression threshold thing is a nice thought but I know for a fact it is doing SOME compression because I can check in a huge file and the size difference of the total LOB will be only marginal.
Thanks for the help, but I ran out of time to determine an answer on this issue.
Not really answered, but also don't have time to spend on it anymore.
DBMS_LOB will show you the file size compressed. If you are not seeing it then post an example showing what you are doing.
I have a working demo at www.morganslibrary.org/library.html under SecureFiles.