Fragmentation

> > > > In the good old days of SE, a table with a high level of activity > > (i.e. deletions/inserts) became riddled with old data row slots > > which were available for re-write, and the index began to look like > > swiss cheese. To correct this periodic unload/loads or cluster > > manipulation or ALTER TABLE (same as an unload/load but more user-friendly) > > were needed to keep index and data table efficiency at peak. > > > > Is this also true of Online? Or does Online do this automagically? > > > Raw Online space does get very fragmented, especially if you are short > of room in the partition. Table extents become very small and numerous > and it causes performance problems. Tables can generally have about > 240 extents, and it is possible to reach that value and come to a grinding > halt. > > We regularly monitor all our production systems extents and partition > fragmention. Tbunloading and tbloading the database back typically puts > all the data for each table in the first extent (if there is enough > contiguous room). We then carefully set all the next extents on the > tables, to accomodate future growth. If tbunloading is unreasonable > because of the database size, we will create an empty new table, with > the first extent set, and copy the data from the old table to the > new table. > > > Thank you, I got a slightly different answer yesterday to wit: ->Online does automatic page compression when it writes disk. the tbstat -p ->command will show the number of compresses that have been executed. see ->page 2-117 in the dba manual (v5.0). -> ->regards, It sounds like you are discussing disk fragmentation which is another HIGHLY viable concern and I thank you for your note. Your welcome. I try to pass on what I have learned from actual experience with the beast. We are currently running Online 4.1 on our production systems. I wonder if 4.1 employs the same technique described in the 5.0 manual. I know there are many features 4.1 supports that were not documented until 5.0. I have the 5.0 DBA manual for a preview and it *is* an outstanding manual. Upon reading the chapter on data compression, it appears to me that they are describing compression within a page, and that information is good to understand. I was speaking in a larger sense about the entire partition. Have fun, Naomi -- Naomi Walker (aka N7FSA) naomi%anasaz.UUCP@asuvax.eas.asu.edu Enthusiasm is caught, In tennis, not taught. love means nothing.