On 07/11/2018 04:01 PM, Ron wrote:
On 07/11/2018 04:10 PM, Christopher Browne wrote:
[snip]
ITIL surely does NOT specify the use of database rollback scripts as
THE SPECIFIED MECHANISM for a backout procedure.
In practice, we tend to take database snapshots using filesystem
tools, as that represents a backout procedure that will work regardless
of the complexity of an upgrade.
It is quite possible for an upgrade script to not be reversible.
After all, not all matrices are invertible; there are a surprisingly
large
number of preconditions that are required for that in linear algebra.
And in databases, not all upgrades may be reversed via rollback scripts.
Does "rollback script" truly mean undoing what you just did in a
transaction-like manner?
Hard to say without knowing the system you are using, but I would guess
no. I use Sqitch and it uses the term revert:
https://metacpan.org/pod/sqitchtutorial#Status,-Revert,-Log,-Repeat
which I think is more accurate. I find it very handy feature when in
development mode. Write script --> deploy --> test, if fails --> revert,
rewrite deploy script --> deploy and so on.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
