A tail of a DMS bug and the curious case of the Endpoint setting ForceLobLookup
So this is a very interesting case that we came across in one of our AWS accounts recently. We are replicating data between a MS SQL Server source to a Aurora PostgreSQL cluster using AWS DMS. The one table being replicated is fairly basic, just some integer and string columns. Below is the definition of…
MS SQL Server Page Storage
So MS SQL Server stores all data in rows that fit onto 8kb pages.There are many different types of pages in MS SQL Server but for this blog we are mainly concerned with three, these are:1. Data Pages2. Text/Image Pages, sometimes referred to as LOB pages.3. Index Pages The names are fairly self-explanatory but for…
Fun with AWS Availability Zone Names and RDS Cloning Across Accounts
Well the above is some mouth full for the title of the blog, but hey, it best describes what I’m going to talk about today. One of the very 1st things I remember learning about when I started my cloud journey into AWS way back in 2018 was about how AWS splits the world up…
AWS DMS Hidden Gotcha’s Part II
Back in March 2022 I wrote a Blog post AWS DMS Hidden Gotcha’s Part I, todays post is a continuation of this outlining some more quirks of DMS that I have become aware of from working with it on a daily basis. Index creation locking system table causes DMS Task to fail: Ok, so this…
Checkpoints logged in Aurora PostgreSQL V.15
One of the changes that came with PostgreSQL V.15 was that the configuration setting log_checkpoints had its default value changed from 0 to 1, meaning that now by default it was on. Ok, so what does this setting actually do? Well it does exactly as the name suggest, it logs all checkpoints that occur in…
What Tech Books am I reading?
Well folks today is a less technical post as I discuss the books that I have read over the last 12 months and those that I hope to get through in the coming year. As we approach the end of the summer here in Ireland, I always think its a good time to review the…
CTE’s in PostgreSQL
So today’s topic is Common Table Expressions in PostgreSQL and how they can differ to CTE’s used in MS SQL Server depending on how you set these up. So I’m a PostgreSQL newbie, coming over from the world of MS SQL Server, the first major version of PostgreSQL I worked on being V11. When coming…
LRU-K Buffer Eviction Algorithm
We know that when it comes to performance in any relational database, memory is king, that is you want to be able to fit as much as your working set into memory because no matter how fast your disks are they will never come close to the access speed of memory. Ok then, given the…
Partially Contained Database’s in MS SQL Server
Contained Databases or (Partially Contained Databases, more on this later) to give them their correct title is a feature in SQL Server that essentially allows you to create a database where all of the components are contained within that database, even the logins, that’s right the logins can exist only in the contained database and…
How PostgreSQL handles out of row storage
The PostgreSQL storage engines uses a fixed page size of 8kb and it does not allow tuples to span multiple pages. So how do they handle large values? Lets read on to find out. So as we mentioned PostgreSQL does not allow a row to span multiple pages, so to be able to handle large…
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