Do not upgrade your database straight away.
The first part of the upgrade should be done using the current tools version. All task before “Updating PeopleTools System Tables” should be done using PT8.48 in your case.
After these steps you can upgrade your database to 188.8.131.52 and migrate to your new platform (PT8.52.12) and complete the PeopleSoft upgrade.
The certification matrix does not show certified database versions below 8.49.
According to following doc the highest db release is 184.108.40.206.0, but this doc is updated last in sep ,2010.
PeopleSoft Enterprise PeopleTools PT 8.48 Certifications [ID 749052.1]
The first step of the upgrade need to be preformed with the current PeopleTools set, described in the ToolsUpgrade manual.
It is easier to run these steps prior to upgrading your database to 220.127.116.11.
Create a copy of production on your current platform, run the steps as described below and after that upgrade your database to 18.104.22.168 and after this migrate your database to your new platform (PT8.52) and complete the rest of the steps of the upgrade script.
That can be a way, but I'm not a fan of big bang. Since the Peopletools upgrade can be tricky, depending of the customizations, I would recommend to avoid to add more complexity in the process, like upgrade Oracle in the middle. If something is going wrong somewhere, it's always difficult to say what is causing it, where it is coming from. You also may have performance issues, due to PTools, Oracle upgrade...
I would try as much as possible to separate upgrades.
First upgrade to the lastest 10g supported within PT8.48, that is also the oldest one supported by PT8.52. Oracle 10.2.0.5 is nothing compared to 10.2.0.4 but a patchset. It should be relatively easy to apply and not a big thing. It should not hurt.
On a second step, follow the entire stream of Peopletools upgrade to 8.52. -- a lot of test should take place
And lastly, upgrade the database to 11g (I would go for 22.214.171.124 instead of 126.96.36.199). -- a lot of test should take place, like performance or known bugs...
One more reason why I would separate the upgrade as much as possible, that's the wordsize support change between your PT8.48 and PT8.52.
You did not say about your current plateform/OS, but bear in mind that PT8.52 is 64bit only. That can raise an entire architecture change in your infrastructure.
=> Upgrade db to 10.2.0.5 on AIX 6.1(Today Its on AIX 5.3 10.2.0.4.0 today)--DBMS Server for Tools 8.48 is supported on AIX 6.1.[We are still Tools 8.48 here]
=>Upgrade Tools to 8.52 ,while DB is still on 10.2.0.5.0.
=>Then upgrade Database to 188.8.131.52.0
=> Then Upgrade application to 9.1 FP2.
Please see if the above looks correct.Please suggests changes accordingly.