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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Calculate PCTFREE and PCTUSED
Bob
The big factor on PCTFREE is your data volatility. If the data is never updated (static), you can reduce PCTFREE to a very small value. But if the data is often updated, chances are you will end up with row migration (usually called row chaining, but that is something different) unless you go with a larger PCTFREE.
PCTUSED controls how quickly a block will be returned to the free list after some data is removed from the block.
If you are looking for a calculation for how many blocks a table will take up, you can do a web search and find several. But I've found it isn't a very precise calculation. Today with disk space easier to come by and DBA time being more scarce, it usually isn't worth going to too much trouble.
I looked in Kevin Loney's book Oracle9i DBA Handbook and he says to allow 90 bytes in each block for overhead, in addition to your PCTFREE.
Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
Sent: Monday, April 21, 2003 11:52 AM
To: Multiple recipients of list ORACLE-L
All
Im looking for a straight forward calculation for PCTFREE and PCTUSED I can total the bytes for all columns or get the average length after running statistics on the table however this is a new (empty) table that will have say 100K rows populated via sqlldr and then an estimated growth of 5000 rows per mon.
I like to know how to set the PCTFREE and PCTUSED manually. Ive read some documents but none to straightforward
Eg col length x col_num * blocksize...?????
TIA!
bob
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Author: Bob Metelsky
INET: bmetelsky_at_cps92.com
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Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services ---------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Mon Apr 21 2003 - 13:06:49 CDT
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