> The system I am using is OpenVMS IA64 v8.4.

   Ok.

> From the command  dump /header /block = end = 0 YOUR_FILE
> out put is File ID (15486,1,0)   End of file block 80 / Allocated 80.

   Is that the only "End of file block" in that report?  (If not, what
is the other one?)

   When you report only the "important" data, you need to know which of
the data are important.  When you report _all_ the data, you don't need
to know as much.

> >    COPY?  BACKUP?  (And what does the other one do?)

> After copying file like :  $ copy/log AGTOFC.IDX;1 AGTOFC.IDX_copy
> The copied file  AGTOFC.IDX_copy is retuning efblk correctly i.e. 80.

   And what about after BACKUP?  (I don't do much with indexed files, so
I know nothing, but I thought that that would be an interesting
experiment.)  "Correctly" here may not be what you think it is.

> I want efblk value for calculating file size.

   Apparently, you do _not_ want efblk for calculating file size,
because you can't trust it (for a non-sequential-access file).  For a
sequential-access file, the End-Of-File mark is significant.  For an
indexed file (which is never processed sequentially), the End-Of-File
mark is not significant, so many programs do not bother to set it.

   Perhaps you really want the allocation quantity.