[OpendTect_Users] Back- and forward compatibility of data

[Bert Bril]

Hi all,


I just got a couple of questions in support about something that pops up 
regularly, so maybe it's a good idea to share it.


First of all, here in our office, we have many many versions installed 
happily side-by-side. The case studies people usually work with one of 
the latest versions, sometimes even with snapshots of the development 
environment.


> Is there a necessity take the data backup before going ahead with
> upgrade/install?

In principle, not. Data and software are strictly separated, and 
whatever version you are running will use the same data store.

Of course we always recommend making backups in case anything goes wrong 
anywhere - I mean how can we take the risk of guaranteeing everything 
goes right?

Maybe interesting to know: we never make data backups when installing a 
new version.


> Once the projects are accessed through the upgraded version of
> OpendTect will it be possible to revert back to the previous version
> in case if we want?

Yes, but there are two things to note:

1) Sessions
Sessions are not actual data, but more a 'snapshot' of what you have 
currently loaded. They are in principle portable within a version, from 
patch to patch. Additionally, we usually succeed the port from one 
version to the next, for example 4.0 sessions are most often usable in 
4.2. But that's it; we cannot go further; 3.4 sessions will probably not 
load well in 4.2.

2) Data incompatibility.
New releases should read all 'old' data; this is really a key issue for 
us. We still have surveys made with 1.x versions that we can use. The 
other way round is not guaranteed. Every major release will introduce 
new types of data, and sometimes format changes. For example, in 4.2 it 
is possible to define 2D line geometries external to the seismic data 
files. If you go back to 4.0, then the 'new' line geometries will not be 
recognized by the 4.0 software and you will see 'old' geometries. But it 
can even be worse: new objects may not be readable by older versions.


Thus: going to a new release does have its 'roll-back' issues - just 
like using a new version of M$ Office will soon produce files that can't 
be used by older versions. If you find these issues unacceptable, make a 
backup of the data.


Bert

-- 
-- Bert Bril / OpendTect developer at dGB
-- mailto:Bert.Bril at opendtect.org , http://opendtect.org