Hello,

Your Understanding on Migrating is completely correct.

However, it is also important you to understand that SEP 11 and SEP 12.1 are 2 different products.

and there are lots of different features which have been added to 12.1 clients

So, SEPM 11 would not be able to update SEP 12.1 clients due to product change.

I would request you to plan Migration properly and go with the Second idea of your's.

i.e; Migrate SEPM and then the clients via AutoUpgrade.

Again, to understand if the SEP clients have been upgraded is very easy.

In the SEPM, change the Clients TAB view to "Client Status", shown below:

Planning for Migration to Symantec Endpoint Protection Manager 12.1

http://www.symantec.com/docs/TECH162730

Steps to prepare computers to install Symantec Endpoint Protection 12.1 client

http://www.symantec.com/docs/TECH163112

Upgrading or migrating to Symantec Endpoint Protection 12.1

Hello,

You don't need to spesific process for upgrading,most of times i don't backup DB also. 

Just start the Setup of 12.1 and follow the screen procedures. This is the easiest upgrade. Because of Embedded DB schema upgrade it'll take much time in the upgrade wizard when your DB Schema being update due to your DB size.

For updating clients, if all clients are in LAN add 12.1 package to top of the group. Else use Push Deployment Wizard.

Regards,

Oykun

Mithun's lnks and info should set you on your way.

Just as an addendum, I think it's worth pointing out the below:

As you are looking to perform an in-place upgrade, there is no need to play around with any sylink files.  Once the in-place upgrade of your SEPM is complete, the SEP11 clients will start talking to the v12.1 SEPM without issue.  Exporting another sylink file and pushing it out to the SEP11 clients serves no purpose.

Once the upgrade is complete and you can see all your SEP11 clients checking into the SEPM, you can start looking at the client upgrade options.  I'd personally go for the auto-upgrade feature which you already seem familiar with.

When using this feature, it is always recommended to only enable it for a group at a time, and to disable the upgrade when all the clients in a group have upgraded (presumably you don't have all 300 clients in a single group!).  Soooo, pick a group, upgrade, check they have upgraded, disable upgrade, and move onto the next group.

Don't forget that you can always schedule the upgrade for specific time windows, as well as spread them across several days if you're really concerned about the load this will place on your network or SEPM.

Finally, as Mithun has mentioned, SEP12.1 adds handy options for checking on the status of client upgrades.  In addition to the 'Client Status' view which shows the current client version, you can double-click on any client to see its deployment status.  The Deployment status is shown when you open a clien't properties in a few fields at the bottom of the 'General' tab, and will show you at what stage of the upgrade the client is in, as well as details on what versions of SEP it is moving to and from, plus when it was last upgraded (as below):

I would like to ask question ?

Your clients are residing on same LAN ? If yes...bandwidth should not be a concern.SEPM won't push upgrade package to all the clients at the same time. However you can schedule your upgrade as per your non production hours.

Check following article

https://www-secure.symantec.com/connect/articles/sepm-121-auto-upgrade

I would like to clear your doubt also, as you said --> Either i can export the communication file of each group in the SEPM after converting it to 12.1 and then go to individually on each machine of the respective group and replace the old sylink file with the newly exported sylink file and then the clients will automatically download their respective package. 

Ans : No manual work is required, we have Sylink replacer utility, it will replace sylink.xml file on all the clients. However I would also suggest to go with Auto upgrade.

To know how upgrade will work, check this article

https://www-secure.symantec.com/connect/articles/sep-11x-sep-121-upgrade-process-graphical-overview

Also, only database backup is not mandatory, follow this article prior to upgrade.

http://www.symantec.com/docs/TECH102333 

I hope it will help you !!!

Thank you every one for replying and making it clear, appreciate it

Kindly tell me one more thing that let's say i've a group in which there are about 40 clients and I go for an autoupgrade the group with the 12.1 package then isn't going to be a network congestion in that Case?

usually it is incremental hence less in size.

Hi Pete,

I think it wont be incremental upgradation as the product changed from 11.x to 12.1. But as per your article (https://www-secure.symantec.com/connect/articles/e...) which is approx 52 MB size and the same can be schedule for auto upgrade.

it's the size after exporting package . While autoupgrade in some scenrio it is full otherwise it is delta. Tested and came around 43 MB of package.

each client will be around 43 MB, i did test from Ru 7 to SEP 12.1. You can test it on client machine, enable sylink logging, once upgrade pass on the sylink log. I can tell you the size of the client package.