When you move or migrate software systems from one platform to another, one of the most important, if not the most important, factor is knowing precisely what you are moving. Yes, this does sound like I'm stating the obvious, but when moving a complex system made up of many interdependent parts, this aspect is often underestimated. While assessing the current system may not seem like a very interesting or technically challenging task, it is vitally important. 

Let me explain why by way of an analogy. You have to move to a new apartment after being in the current one for several years. Over the years, you have accumulated quite a lot of furniture and belongings that are very well suited to your current residence. For example, you have a corner lounge suite and a large two-sided home office desk that also fits into a room's corner as you work from home several times a week. You have a large tropical fish tank, a home gym, and an enormous collection of records that you like to play loudly on a high-end record player. As well as these large items, you have a multitude of kitchen appliances and draws and shelves, some of them built into the walls, storing clothes and knickknacks. You head out to look at prospective new apartments, keeping in the back of your mind an approximate mental inventory of all your stuff. There are quite a few factors you need to keep in mind when looking at a new property that is analogous to a migration scenario. With regards to the target environment, not only does it need to have the space to accommodate all your stuff, that is, storage and compute, but it needs to be able to meet unique storage requirements.

Are there corners for the lounge suite and desk? Compliance - Is the floor strong enough to take the fish tank's weight, and is it away from direct sunlight?  Network – does the apartment internet connection have sufficient bandwidth for you to work from home? Backups – is there enough built-in shelving and storage for all your records and stuff? Security – does the apartment have sufficient soundproofing so you won't disturb neighbors with music or be disturbed by external sound when working. Yeah, I know I'm reaching a bit with that one. Next, we come to the move or migration itself. Without an accurate assessment of how much stuff you need to move, how will you know what size truck to hire and how many movers you will need to lift and carry? Does the new site have a service elevator to bring up the large items, or will you have to break them down, or worse, crane them in or leave them behind? Anyway, you get my point that not only is an inventory of the current state important, but it must be accurate both qualitatively, that is what exactly you have, and quantitatively – how much you have. 

On the minus side of the inventory ledger, SAP systems are complex and made up of many securely interconnected nodes and components. On the plus side, SAP is very prescriptive from a hardware point of view, so sticking with certified components limits your chances of getting it too wrong. As I've alluded to, several elements make up an SAP system or elements that SAP is dependent on. We need to catalog database and application servers with their respective software versions. We will need a description of the network topology and associated security features such as firewalls, gateways, and proxies. What system and database backup functions are in place, and what is the nature of the high availability and disaster recovery mechanisms? For all these elements, we will need performance metrics to ascertain CPU and memory load, as well as storage requirements and network throughput and latency. These numbers will be instrumental in determining the new landscape size and design.