Datafile Header

Hi,


I am wondering how much space will be allocated for a datafile header, also will this differ the way the tablespace is managed(Dictionary or Local).

Thanks

select FILE#, BYTES from V$DATAFILE_HEADER;

hi julian,
That will not give you the header size of the datafile..but infact the whole size
I really doubt if you could actually find the header size of the datafiles which could be OS dependent.
Cheers

You are right. The query returns in fact the size of the datafile. I also doubt if you could find the header size of the datafiles. Who needs such an information :-)

Hi,

I was doing some research and came across the file header size.

Never mind i will try to find out..

Thanks

if you have tablespace manager you can see that 2 blocks is reserved for the overhead, now I am not sure what happens if you have several datafiles, AFAIK they are still 2 blocks but I have only checked this with small tablespaces, may be someone else have tried with larger tablespaces?

In localy managed tablespaces file header is definitely larger than 2 blocks. For LMT file header includes a bitmap for extents, and this bitmap is allways 64K in size, regardless of the block size.