Re: dbexport/dbimport problems

Some previous communications on this subject deleted. > > Someone has borrowed my OnLine admin manuals, so I can't RTFM. > > 1. Is there a way to place a table's index in a dbspace other than the > dbspace containing the table, presumably on a different disk? > ANSWER - NO - there is no way of controlling where the index goes in OnLine. > Offhand I would think this is a good idea. On long queries sorted by > the index (a recommended strategy), one disk would read the index while > the other read the data, reducing head contention. In the example you > give, if the LOAD mixes the data and index pages then you get most of > the same effect, but there might be a bit of thrashing during disk > transitions. If you can put the index into a different dbspace, this > would make the performance more uniform over dbimport vs. load. ANSWER - this would indeed be a useful facility. But without any control it could only be achieved if you knew definite data sizings and set chunk sizes accordingly - loaded the data and then created the index into a separate chunk. BUT IF THE DATA VOLUME CHANGED??? > > 2. Do Informix's indexes tend to be "deep" or "wide"? > > Your 5 index reads per data read seems high to me, unless the table is > REALLY big, thus making even "wide" indexes into "deep" ones as well. > Even with deep indexes, wouldn't the first few levels stay in the cache, > reducing the physical reads to only the lower levels for subsequent > index searches? ANSWER - I too was surprised at David's 5 index reads for one data read. He was however quoting from experience on a VERY LARGE (50million record) table. As to whether the index is deep or wide I think that it depends on index field size. But I wouldn't be completely sure. Malcolm Weallans Online Database Consultancy 2 Arkley Court Maidenhead Berks SL6 2YR Phone 0628-72154 Fax 0628-37463 CIX - onlinedbc