Hi Christian, Considering that the update frequency is very low: only a few hundred times per week, and that the total size of the information is also very small (you said about 20,000 employes: considering 100 bytes per employee, this makes around 2 MBytes), I would recommend - to use the TFolder structure in memory with the hierarchy as you described it in your original mail. - to write the top folder with folder->Write at each transaction as a new key in the same file or in a different file. The time for one transaction should be below 1 second. Rene Brun On Sat, 12 Jan 2002, cstrato@EUnet.at wrote: > Dear Rene > > Thank you for your reply, here is what I intend to do: > I want to create a TFile, which should organize experiments in a > hierarchical structure. The “employee” folder should contain references > to TTrees and some additional information as objects. The TTrees > themselfs containing the data will be stored in different TFiles. > Access to the TTrees should be handled from this main file. > The update frequency is low, e.g. hundred experiments per week each > containing about hundred TTrees. > > Although some of your slides suggest MySQL as Run/File catalog for > the Event Store I must admit that I do not believe in RDBMS. > Browsing the book “The Object Data Standard: ODMG 3.0” from the > members of the ODMG, one can see that most classes described in the > book are already implemented in ROOT. One of the few classes missing > is class TTransaction {begin(), commit(), abort()}. > I have already started to implement this class in a way which is > sufficient > for my purposes, and it seems to work fine. > > My main problem is to implement a hierarchical structure in the main > file which is not only browsable but also searchable. > > Best regards > Christian > > > Rene Brun wrote: > > > Hi Christian, > > > > It is difficult to give you an advice without knowing a more > > precise configuration and access patterns. > > What is the update frequency? one per millisecond, second, month ? > > What is the real population in each node? > > > > It is also not clear to me what are the operations you need to > > perform: in memory only, on disk only, on both. > > > > ROOT I/O is not an alternative to a pure conventional relational > > data base to describe eg, employee/organisation type of relations. > > May be a tool like MySQL is more adapted to this task. > > > > Rene Brun > > > > On Sun, 6 Jan 2002, cstrato@EUnet.at wrote: > > > > > Dear Rooters! > > > > > > Maybe you can give me some advice whether to use TFolder or TDirectory > > > when storing large amounts of TObjects in a TFile. > > > > > > > > Thank you in advance > > > > > > Best regards > > > Christian > > > ---------------------------------- > > > C.h.r.i.s.t.i.a.n S.t.r.a.t.o.w.a > > > V.i.e.n.n.a, A.u.s.t.r.i.a > > > > > > >
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