On Thu, Jul 28, 2016 at 6:32 PM, Alex Ignatov <a.igna...@postgrespro.ru> wrote:
> > On 28.07.2016 18:41, Igor Neyman wrote: > >> -----Original Message----- >> From: Alex Ignatov [mailto:a.igna...@postgrespro.ru] >> Sent: Thursday, July 28, 2016 11:26 AM >> To: Igor Neyman <iney...@perceptron.com>; Rakesh Kumar < >> rakeshkumar46...@gmail.com> >> Cc: PostgreSQL General <pgsql-general@postgresql.org> >> Subject: Re: [GENERAL] Uber migrated from Postgres to MySQL >> >> >> On 28.07.2016 18:09, Igor Neyman wrote: >> >>> -----Original Message----- >>> From: pgsql-general-ow...@postgresql.org >>> [mailto:pgsql-general-ow...@postgresql.org] On Behalf Of Alex Ignatov >>> Sent: Thursday, July 28, 2016 10:59 AM >>> To: Rakesh Kumar <rakeshkumar46...@gmail.com> >>> Cc: PostgreSQL General <pgsql-general@postgresql.org> >>> Subject: Re: [GENERAL] Uber migrated from Postgres to MySQL >>> >>> >>> On 28.07.2016 17:50, Rakesh Kumar wrote: >>> >>>> On Thu, Jul 28, 2016 at 10:38 AM, Alex Ignatov < >>>> a.igna...@postgrespro.ru> wrote: >>>> >>>> Sorry, what? You can rollback to previous version of software what you >>>>> had. >>>>> >>>>> https://docs.oracle.com/cd/E11882_01/server.112/e23633/downgrade.htm >>>>> # >>>>> UPGRD007 >>>>> >>>> Not so fast. This requires the db to be set in compatibility mode of >>>> the lower version. Once that is removed, no downgrade is possible. >>>> >>>> Also starting from Oracle 12 this downgrade option has been removed. >>>> That is, you can't upgrade in-place from Or 11 to 12 and then >>>> downgrade back. The only supported way is the restore from an old >>>> backup (which is true for all products). I don't work in Oracle, but >>>> got this clarified by someone who is an Oracle dba. >>>> >>>> >>>> Not true - >>> >>> https://docs.oracle.com/database/121/UPGRD/downgrade.htm#UPGRD007 >>> >>> About compatible params you are right but downgrade is possible from 12c. >>> >>> Alex Ignatov >>> Postgres Professional: http://www.postgrespro.com The Russian Postgres >>> Company >>> >>> ______________________________________________________________________ >>> _______ >>> >>> Alex, documentation you point to just proves what Rakesh said: >>> >>> "For supported releases of Oracle Database, you can downgrade a database >>> to the release from which you last upgraded. For example, if you recently >>> upgraded from release 11.2.0.4 to Oracle Database 12c, and you did not >>> change the compatible initialization parameter to 12.1 or higher, then you >>> can downgrade to release 11.2.0.4." >>> >>> So, you can downgrade only if you didn't "activate" newer feature >>> (didn't compatibility to higher version). >>> But then, what's the point in upgrading (I know, there are some like bug >>> fixes, etc...), if you aren't going to use newer features. >>> >>> Regards, >>> Igor >>> >> Not true again. >> >> From Oracle docs >> https://docs.oracle.com/database/121/UPGRD/intro.htm#UPGRD001 Section >> "How the COMPATIBLE Initialization Parameter Operates in Oracle Database" >> - >> If you run an Oracle Database 12c database with the COMPATIBLE >> initialization parameter set to 11.0.0, then it generates database >> structures on disk that are compatible with Oracle Database 11g. >> Therefore, the COMPATIBLE initialization parameter enables or disables >> the use of features. If you try to use any new features that make the >> database incompatible with the COMPATIBLE initialization parameter, then an >> error occurs. However, any new features that do not make incompatible >> changes on disk are enabled. >> >> So if feature do not change disk in incompatible way this features is >> enable. >> >> Also from this >> >> https://docs.oracle.com/database/121/REFRN/GUID-6C57EE11-BD06-4BB8-A0F7-D6CDDD086FA9.htm#REFRN10019 >> : >> >> "This parameter specifies the release with which Oracle must maintain >> compatibility. It enables you to take advantage of the maintenance >> improvements of a new release immediately in your production systems >> without testing the new functionality in your environment. Some features of >> the release may be restricted." >> >> So this parameter is made with rollback in mind and you have some new >> feature from newer software release. >> >> Alex Ignatov >> Postgres Professional:http://www.postgrespro.com >> The Russian Postgres Company >> >> >> ____________________________________________________________________________________________________________________ >> >> B.t.w., In Postgres release which doesn't change "database structures" >> is called "minor" (just replacing binaries), and allows downgrade. >> >> "Compactable" or not, in "Oracle world" no DBA in their right mind will >> attempt major upgrade without having complete (and tested) backup that >> could be used in case of upgrade going wrong. >> >> Regards, >> Igor >> >> Oh, so in contrast to "Oracle world" "Postgres world" DBA in their > right to do major upgrade without complete and tested backup? > Ok, I understand you. In Postgres world there always sky is blue and sun > is shining. And see, I am just wondering, what DBA in their right mind would allow a db to run without a complete and tested backup. I mean when you upgrade the last thing you do is take another backup and the first thing you do after upgrading is take another backup, right? Or am I just being dense?
