Re: Good DBA please give some technical understanding....

header with such things as keys ?
does oracle provide information on their hashing algorithms ? have i missed something here ?

"Barbara Kennedy" <barbken_at_teleport.com> skrev i en meddelelse news:yD4Q5.10923$au.473779_at_nntp3.onemain.com...
> Blocks are read in their entirety and written in their entirety. There is
 a
> header (small) in each block that holds the info about the block. There
 are
> chapters on how it decides to write to a block that has data or a new one.
> "Damian" <kndoneill_at_hotmail.com> wrote in message
> news:Yc3Q5.31536$SF5.552348_at_ozemail.com.au...
> > For curiosity's sake, I'd like to see the source code (fat chance I
 know).
> > Therefore, as an exercise in reverse engineering, how would one go about
> > updating a dbf file?
> >
> > SELECT Scenario
> > Selects, updates and deletes would first require a file seek function. I
> > quess you'd have to do a string search first to find the rowid.
> >
> > UPDATE Scenario
> > Well I guess you'd open the dbf with file read, write flags set.
> > Then you'd search thru the file sequentially, probably moving your file
> > pointer every <block size> until you found your table from the table dir
> > then row from row dir. Then delete <ROWID> from block, (then maybe) move
 all
> > data in block after the deletion up to where the rowid before the
 deleted
> > one ends. finally, write your updated row at the end of the last row in
 the
> > block.
> >
> > INSERT Scenario
> > Say a new row is to be inserted into the table.Is it going to be
 inserted
 at
> > the END of block (which?) assigned for the Table. What will happen if
 the
> > Block is consumed and a new block is going to be created. Where the new
> > block is going to be created and how it will effect the performance when
 the
> > blocks are split across separated by different blocks.
> >
> > DELETE Scenario:
> > Same as update without the write function at the end.
> >
> > "Barbara Kennedy" <barbken_at_teleport.com> wrote in message
> > news:D61Q5.10839$au.438196_at_nntp3.onemain.com...
> > > If you are just looking for it conceptually the manual (available in
 Html
> > > format on the CD ) Oracle Concepts manual. If you are asking so you
 can
 get
> > > at the data directly then don't do it! If you need to get at the data
> > > directly (by scanning the file directly) write your own dbms; don't
 use
 a
> > > commercial dbms and try to subvert it. You will only cause yourself
 great
> > > pain. The manuals don't go into enough details to reverse engineer
 it.
> > > Jim
> > > "Pravesh Godiyal" <namia_at_hotmail.com> wrote in message
> > > news:Sj0Q5.31459$SF5.549328_at_ozemail.com.au...
> > > > Is there any one aware or could share the knowledge as how oracle
 store
 the
> > > > table-reocrds into dbf files.
> > > > How it access the data in the dbf files.
> > > >
> > > > Cheers
> > > > Namia
> > > >
> > > >
> > >
> > >
> >
> >

>
> Received on Tue Nov 14 2000 - 01:35:31 CST