On the occasion where you replace your system with a new system, move your system to a data centre or even move your system to a new geographical location, a system migration takes place.
Typically, a system migration takes care full planning, testing and a lot of coffee.
In a classic IBM system migration, the migration is mostly started by outlining the OS releases of the source and the target system. Next is making a full system save (option 21) on the system (source) and restoring this save on the new system (target).
After restoring, the testing of the newly created system takes place and if all goes ok, your scenario for migrating is ready.
In the final migration, you rerun these steps until you're satisfied with the results and a switch to the new system can take place.
Easy. Or not?
When you go in more detail in above scenario, decisions about the OS release have to be made. Upgrade the source system OS to the target system OS? Downgrade the target OS to source OS? And how about the hardware support?
You will quickly notice that making a full system save requires the IBM system to be in 'restricted mode'. Restricted mode means the system is busy doing only 1 thing: making the full system save. This is a needed procedure to make sure all objects are unlocked and not changed during the time of the full system save to ensure your backup is an exact copy. The full system save contains a full copy of the system including system objects, applications and local data area.
Restricted mode also means, users can't work on the IBM system or access any data while the save is in progress. Therefore, a full system save has to be planned outside production hours or a scheduled production downtime has to be made which brings extra (hidden) costs.
Depending on the size of the system, this can be done in an automated process overnight or for larger companies in the weekends when the production is down.
In this way, when having a production environment which continuous for 24/7 and 365 days a year, getting your system in restricted mode can be a real challenge.
When you are ready to actually switch to the new system, you make a final data save and restore it directly to the new system. Again the source system and the new system need to be in restricted mode to make a consistent backup.
After restoring this data save you need to make a final test before you take this system in production. During this process, the production is down.
The full system save and restore can take up many hours. This is where the coffee comes in.
Remember, doing a full system save brings down your entire system until it's finished, you can only access your IBM system through a console session. Make sure you are able to access the console when needed.
When the full 'system save' is completed, the media where the full 'system save' is placed on needs to be transferred to the new system. This is easily done when the system is in the same building or nearby, but what if your system you want to migrate to is in a different country, overseas or even on a different continent...
More info on a full system save on IBM i on the IBM documentation website
Using a High Availability solution for migration
Nowadays there are more solutions for migrating a system. One of the easiest and most cost effective solutions is to rent and use an HA (High Availability) software solution. With an HA solution you replicate the source system to the new target system and after the complete replication you switch the production from source to the target system.
You can setup the replication between the 2 systems without stopping the production on the source system. You don't even need the same OS release on the 2 systems.
When using an HA solution, you first bring the 2 systems in sync, then, after testing and adjusting the replication, you can switch to the new system at any time with just a very minimum of downtime and start your production process from the newly created system.
Whether your target system is in the same room, same building, overseas or on the other part of the world... it does not matter. Having an advanced HA solution uses just little bandwidth and you 'll only need a working and stable TCP/IP connection between the two machines.
So, how is this accomplished?
QSL group developed an HA software solution which is able to exactly replicate a partition to another partition (except the OS). We start by installing our high availability solution Quick-EDD/HA on both machines. We only require the OS to be installed on the target machine and therefore a full restore from tape is not needed.
Then we can setup the full sync from scratch so all data is sent from the source machine to the target machine, building up an exact copy of your original system (libraries, system objects, IFS, spool & Sysval). If the sync is complete, we continue replicating, on bit level, so any change that occurs on the source machine will be implemented on the target machine thus keeping both systems perfectly synced.
Based on net-change technology, only the differences are replicated. As an example, when there is a recordset of postal addresses and the house number changes, only the house number will be replicated to the target system and implemented there. The (re-)sending of the whole record set is avoided.
In this way, the high availability replication uses very low CPU and little bandwidth. Your users won't even notice there is an HA replication running on the system!
When all testing is done on the target machine, we run a verify to ensure the data between the 2 systems is consistent. When the verification is complete and successful, you are able to switch to the target with our switch scenario. Our technical staff will help to smooth out this process as easy as possible.
To migrate a system to another system, and there is no need to buy HA software for further and continuous replication, you can also rent our software for the desired time.
Our staff is happy to guide you with the proper timelines or provide reference cases.
Quick-EDD/HA is a high availability solution from the quick-software-line from Trader's, France.
Trader's has a worldwide reputation for advanced replication services and develops and implements HA, document and security software solutions for IBM i.
QSL Northern Europe distributes the quick-software-line in the Netherlands, Germany, United-Kingdom, Scandinavia and Austria through her selected partners.