InTerBase batabase file ?

[jone]

Who know,Why the zise of database file is be reduced when restore it from a back-up database file ? ( Ex. befor backup the zise is 13 MB, after restore thse size is 9 MB), but I saw every thing worked well ?

[MartinOaktree]

Hi,

when You have delete some datarows, the filespace is only marked as delete, when you store new DataRows, then this Space is used, but when you backup the Database and restore it,
then the deleted space is not restored!

So if You delete many Rows, and insert no new Rows,
then the Size of Database-file is decreased.

Hope this helps.

Martin

[jone]

is there any way to config the Interbase to really remove deleted record ?

[MartinOaktree]

Hello,


Interbase (and all other Database-Systems) use a normal file to store the Data, and the Operating-System in this case Windows (NTFS Win-NT,2000 or Dos-FAT Win 95,98,ME)cannot decrease the Filelength. A File can only added (Append) Data at the end of the File or the Data can be changed a any Position in the File.
For Example:
It is possible that You have a Databse with 10 rows, and if You delete Row 2,3 and 6 then the Filesystem do not know how to free the Space! (This is only a simple view of the problem, in the Database-file the things are much more complex).

When You insert new Rows, the free Space is used first bevor appending new Space at the end of the File.

When You make a Restore the a new File is created, and in this new File are only the requied Data. But the internal Pointers of the Data are diffrend to the previus File, but this is the Job of the Database (Interbase), You dont need to think about it while using Interbase.





Hope this helps,

Martin

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