> -----Messaggio originale----- > Da: Przemyslaw Czerpak [mailto:dru...@acn.waw.pl] > Inviato: martedì 26 gennaio 2010 20.05 > A: Harbour Project Main Developer List. > Oggetto: Re: R: [Harbour] CDX RDD question (live usage/compatibility) > > 1 works like CL52/CL53 DBFNTX if you do not link ntxlock.obj with > your code.
Now it's clear. > The name is confusion. These .obj files change collation order in > Clipper VM and all index formats not omnly NTX. Yes. I know that. > > The feel i receive from your message is that i'm going in a puzzled > > challenge, so i think i'll have two options: > > A) To leave the Cl52+DBFNTX app, working well from twenty > year ago, and > > to change the driver of Harbour to DBFNTX > > It's possible. > > > B) To take the courage of replace with Harbour+DBFCDX all > the install > > It's probably safer method. > Anyhow as long as some network transport > layer does not cause some separate buffering which can cause problems > when DOS and Windows applications access files concurrently then it > should be safe to share database files and indexes between Clipper > and Harbour. It's enough to set compatible national sorting > and locking > schemes. > > > I don't know the effectiveness of the DBFNTX in Harbour, so > i ask you > > if also the A) choice is dangerous and the pure Harbour > path is the only > > affordable. > > In Harbour DBFNTX is probably much faster then in Clipper and for sure > they can be used to index realy big tables (I know that some people > use Harbour only to reindex files for Clipper due to huge > speed differnce > and the fact that over some size limits Clipper begins to GPF during > indexing). Harbour DBFNTX implementation also supports all > CDX extensions > and few others but you will not be able to enable all of them > if you want > to share data with Clipper. Compound index, large NTX file > support up to > 4TB or using RECNO as hidden part of index key to eliminate > linear scan > during record updating in indexes uses keys with big number > of repeated > values are extensions which change index formats and I > implemented them > only in Harbour and xHarbour so only in these languages can operate on > such NTX indexes. > Technically NTX format is much faster then CDX. In the ideal > environment > where you have a lot of RAM and you can keep index files in memory CDX > is many times slower then NTX. But we are not leaving in > ideal world and > in most of cases indexes are accessed using slow network connections. > It means that the size of index files will determinate the speed. CDX > files store keys in leaf nodes in compressed form what greatly reduces > the total index size and it's the reason of better overall performance > when the cost of reading/writing from/to index file is very big, i.e. > files are stored on file server. Your technical analysis is very useful and only now i realize that the NTX rdd is expanded in Harbour. A quick view on whatsnew.txt told me that was present yet in version 0.46. Anyway, the Harbour CDX install on all clients could be the safer choice, as you say. Again my great thanks for your support and kindness. Best regards. Maurizio _______________________________________________ Harbour mailing list (attachment size limit: 40KB) Harbour@harbour-project.org http://lists.harbour-project.org/mailman/listinfo/harbour
