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From: Raj <rajeshkumar.dba09@gmail.com>
Date: Mon, 1 Dec 2025 14:07:46 +0530
Message-ID: 
 <CAJk5AtYYmxWH6Tbp-3dAiMKd3Ynu4J6ajtOc48rKsa1s3Kk0SA@mail.gmail.com>
Subject: Re: Migration from MSSQL to POSTGRESQL
To: Tayyab Fayyaz <tayyab.humayl@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>,
	Pgsql-admin <pgsql-admin@lists.postgresql.org>
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Sorry, it's Oracle to POSTGRESQL migration.

I apologize for the confusion.

Please suggest based on Oracle.

On Mon, 1 Dec 2025, 14:00 Tayyab Fayyaz, <tayyab.humayl@gmail.com> wrote:

> Hello Raj,
>
> It really depends on how much of those 64 vCPUs and 250GB RAM your SQL
> Server actually uses today, and whether you=E2=80=99re running on a physi=
cal box or
> a virtual machine.
>
> PostgreSQL doesn=E2=80=99t have a 1:1 sizing formula against SQL Server. =
I=E2=80=99d first
> look at real CPU/memory usage, workload pattern (OLTP vs reporting), and
> how connections/queries behave. I=E2=80=99d also factor in how well we ca=
n migrate
> and map the data types and queries, because good type choices and query
> rewrites can significantly reduce resource usage.
>
>    -
>
>    *If it=E2=80=99s a physical server*, I=E2=80=99d start with similar ha=
rdware for
>    PostgreSQL and then tune Postgres parameters (shared_buffers, work_mem=
,
>    etc.) based on monitoring.
>    -
>
>    *If it=E2=80=99s a VM*, I=E2=80=99d provision a bit more capacity than=
 the current SQL
>    Server allocation to give some headroom for tuning and unexpected over=
head,
>    and then right-size after observing the real load in PostgreSQL.
>
> Once the migration is done and in steady use, we can monitor CPU, memory,
> and I/O in PostgreSQL and then optimise or scale down/up based on real
> metrics instead of guessing up front.
>
>
> Tayyab
>
> On Sun, Nov 30, 2025 at 11:14=E2=80=AFPM Laurenz Albe <laurenz.albe@cyber=
tec.at>
> wrote:
>
>> On Mon, 2025-12-01 at 08:46 +0530, Raj wrote:
>> > I am migrating from MSSQL to POSTGRESQL. In MSSQL, I am using 64 vCPU
>> and 250GB RAM.
>> > Now how much we can give in postgres?
>>
>> If these specifications worked for you with Microsoft SQL Server, use th=
e
>> same
>> with PostgreSQL.  If you can, don't use Windows.
>>
>> Yours,
>> Laurenz Albe
>>
>>
>>

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<div dir=3D"auto">Sorry, it&#39;s Oracle to POSTGRESQL migration.=C2=A0<div=
 dir=3D"auto"><br></div><div dir=3D"auto">I apologize for the confusion.</d=
iv><div dir=3D"auto"><br></div><div dir=3D"auto">Please suggest based on Or=
acle.</div></div><br><div class=3D"gmail_quote gmail_quote_container"><div =
dir=3D"ltr" class=3D"gmail_attr">On Mon, 1 Dec 2025, 14:00 Tayyab Fayyaz, &=
lt;<a href=3D"mailto:tayyab.humayl@gmail.com">tayyab.humayl@gmail.com</a>&g=
t; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 =
.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div dir=
=3D"ltr">Hello Raj,<div><br></div><div><p>It really depends on how much of =
those 64 vCPUs and 250GB RAM your SQL Server actually uses today, and wheth=
er you=E2=80=99re running on a physical box or a virtual machine.</p>
<p>PostgreSQL doesn=E2=80=99t have a 1:1 sizing formula against SQL Server.=
 I=E2=80=99d first look at real CPU/memory usage, workload pattern (OLTP vs=
 reporting), and how connections/queries behave. I=E2=80=99d also factor in=
 how well we can migrate and map the data types and queries, because good t=
ype choices and query rewrites can significantly reduce resource usage.</p>
<ul>
<li>
<p><strong>If it=E2=80=99s a physical server</strong>, I=E2=80=99d start wi=
th similar hardware for PostgreSQL and then tune Postgres parameters (share=
d_buffers, work_mem, etc.) based on monitoring.</p>
</li>
<li>
<p><strong>If it=E2=80=99s a VM</strong>, I=E2=80=99d provision a bit more =
capacity than the current SQL Server allocation to give some headroom for t=
uning and unexpected overhead, and then right-size after observing the real=
 load in PostgreSQL.</p>
</li>
</ul>
<p>Once the migration is done and in steady use, we can monitor CPU, memory=
, and I/O in PostgreSQL and then optimise or scale down/up based on real me=
trics instead of guessing up front.</p></div><div><span style=3D"color:rgb(=
0,0,0)"><br></span></div><div><span style=3D"color:rgb(0,0,0)"><br></span><=
/div><div><span style=3D"color:rgb(0,0,0)">Tayyab</span></div></div><br><di=
v class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sun, Nov 3=
0, 2025 at 11:14=E2=80=AFPM Laurenz Albe &lt;<a href=3D"mailto:laurenz.albe=
@cybertec.at" target=3D"_blank" rel=3D"noreferrer">laurenz.albe@cybertec.at=
</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:=
0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">=
On Mon, 2025-12-01 at 08:46 +0530, Raj wrote:<br>
&gt; I am migrating from MSSQL to POSTGRESQL. In MSSQL, I am using 64 vCPU =
and 250GB RAM.<br>
&gt; Now how much we can give in postgres?<br>
<br>
If these specifications worked for you with Microsoft SQL Server, use the s=
ame<br>
with PostgreSQL.=C2=A0 If you can, don&#39;t use Windows.<br>
<br>
Yours,<br>
Laurenz Albe<br>
<br>
<br>
</blockquote></div></div>
</blockquote></div>

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