Re: [nv-l] Compress database Directory

[James Shanks <jshanks@us.ibm.com>]

Tar doesn't break anything.  It's just dumb and wastes space, not when you create the tar file but when you restore it.  Your restored database will typically use more space than it did when it was tar'd up.

NetView databases in UNIX are what are known as a sparse file system.  The items in them are pointed to by pointers in a directory file.  Typically these are widely spaced numerically.  When the untar occurs, tar actually allocates file space for all the entries between the existing pointers, space which may never be used.   Because of this we have always recommended that when you restore, you use pax rather than tar, because pax is smart enough to understand the sparse file system and not use more space than he needs.  Of course, if you have a lot of disk space this is not an issue, and with the use of nvTurbodatabase, which now automatically compresses the sparse files on startup, the whole thing is probably moot.  I haven't looked into it in quite a while.

But  if you are on an older version or you just want to play safe and save your disk space,  if you do, for example, 
 tar  -cvf  mybakup.tar   /usr/OV/databases/openview
to create your backup, then do 
 pax   -rp  e  -f  mybakup.tar
to restore it.


James Shanks
Level 3 Support  for Tivoli NetView for UNIX and Windows
Tivoli Software / IBM Software Group

"Bursik, Scott {PBSG}" <Scott.Bursik@pbsg.com> Sent by: owner-nv-l-digest@lists.us.ibm.com 10/14/2003 03:31 PM Please respond to nv-l

To:        "'Nv-L (nv-l@lists.us.ibm.com)'" <nv-l@lists.us.ibm.com>         cc:                 Subject:        [nv-l] Compress database Directory

NetView 7.1.3 AIX 4.3.3

I am doing some trouble shooting on one of my NetView servers and I am
getting ready to restart automatic map generation but before I do I want to
back up my databases directory. I remember someone telling me not to use tar
on the databases because it can damage them. Is that true and if it is, what
should I use?

Thanks,

Scott Bursik
PBSG