DUMP(V)                      5/15/74                      DUMP(V)


     dump - incremental dump tape format


     The dump and restor commands are  used  to  write  and  read

     incremental dump magnetic tapes.

     The dump tape consists of blocks  of  512-bytes  each.   The

     first block has the following structure.

     struct {

             int     isize;

             int     fsize;

             int     date[2];

             int     ddate[2];

             int     tsize;


     Isize, and fsize are the corresponding values from the super

     block  of  the  dumped  file system.  (See file system (V).)

     Date is the date of the dump.  Ddate is the incremental dump

     date.   The  incremental  dump  contains  all files modified

     between ddate and date.  Tsize is the number of  blocks  per

     reel.  This block checksums to the octal value 31415.

     Next there are enough whole tape blocks to contain one  word

     per  file  of the dumped file system.  This is isize divided

     by 16 rounded to the next higher integer.   The  first  word

     corresponds  to  i-node  1,  the  second to i-node 2, and so

     forth.  If a word is zero, then the corresponding  file  was

     not dumped.  A non-zero value of the word indicates that the

     file was dumped and the value is one more than the number of

     blocks it contains.

     The rest of the tape contains for each dumped file a  header

     block  and  the  data  blocks  from  the  file.   The header

     contains an exact copy of the i-node (see file  system  (V))

     and also checksums to 031415.  The number of data blocks per

     file is directly specified by the control word for the  file

     and  indirectly  specified  by  the  size in the i-node.  If

     these numbers differ, the file  was  dumped  with  a  `phase



     dump (VIII), restor (VIII), file system(V)