As most people don't seem to be able to look up old topics here are the details of last Server Merger and there's no real reason to expect the upcoming ones to be any different on most of the points.
http://www.lineage2.com/en/news/announcements/03222016-shilen-magmeld-and-bartz-server-merge-guide.php
A server merge is a complicated process, and this guide is designed to cover most questions that may come up. If you still have questions after reading this guide, please visit the forums here.
To Prepare for the Server Merge
Delete Characters to Seven or Less: Due to the character limitations per server, only seven characters will be allowed. The easiest way to prepare for the server merge so that you have the most control of the process is for you to delete your own characters. If you have multiple characters on Shilen, Magmeld, and/or Bartz you will need to reduce the total number to seven total characters. Figure out which among your characters you will delete, empty those characters if you wish, and set them to be deleted. Character deletion is a one-day process, but set-to-delete characters will not be included in the merge process, so you will have nothing to worry about.
Check In-Game Mail: All character mail, including those with attachments, will transfer. However, it's still advised for you to check and claim any unread mail.
Collect Item Broker Proceeds: Item Broker sale proceeds will be deleted during the merge. Collect all auction sale proceeds prior to April 13th, 2016 to avoid losing them.
Clear out Clan Warehouse: Only Adena stored in the Clan Warehouse will be transferred. All other items must be removed. Any items left in the Clan Warehouse during the merge will be unrecoverable.
After the Server Merge
After the merge, many game systems will be reset, though some will not. Below is a list of what will be reset or changed:
All characters from Shilen, Magmeld, and Bartz will be moved to the nearest town.
All mail, including those with attachments, will transfer in tact. However, it's still advised to check and claim any unread mail.
All unique-colored names from Battle Tournament will be reset.
Cursed weapons, and the in-game community board will all be reset.
Item Broker sale proceeds will be deleted. Collect all Item Broker sale proceeds prior to the merge.
Any unsold/unpaid for items in the Auction House will be moved to your character warehouse and the related commission will be deducted. Make sure to collect all items from the Auction House before the merge.
Items that are waiting to be sold before the server merge will be moved into the character warehouse and the related commission will be deducted.
Pet names will be reset.
Friend lists and ignore lists will transfer.
Raid points will be transferred.
In-progress clan wars will be ended as a tie.
Alliance information will not be transferred.
Inventory and private warehouse items for all characters that are successfully transferred will remain intact.
All items from the Dimensional Merchant will be transferred. If you'd like to make sure your items will transfer, it's advised to make sure you log in to the game at least once after purchasing the item.
PVP, PK, and Karma points for all characters that are successfully transferred will remain the same.
Character titles will not be reset.
New character creation will be limited on the new server for a short time after the maintenance. New character creation will be available after April 15th, 2016.
New character creation on Shilen, Magmeld, and Bartz will be disabled starting on April 6th, 2016.
Server transfers will be disabled from March 30th, 2016 until April 20th, 2016.
The Merge Process
Below are the steps for the server merge:
1. Character Queued to Merge (Unless Set to Be Deleted)
All characters from Shilen, Magmeld, and Bartz will be queued to merge to the new server, unless you have set a character to be deleted. (Characters that are queued to be deleted before the server merge will be deleted successfully beforehand and will not interfere with your other characters' slot consolidation). Your characters now undergo a series of tests to select the top seven characters (those that will remain after the merge).
2. Characters Reduced per Account to Seven Slots for the New Server
Should you choose not to delete your own characters, we will determine which are kept based on experience.The seven characters with the highest amount of experience (character level and percentage through that level) are kept and transferred to the new server. The rest are deleted. In cases where a seventh and eighth character have the same amount of experience, the older character is deleted to reduce the number of characters to seven on a server. If you have two characters in this situation and you wish to keep the older character, log in and get a little more experience in the character you want to keep. To have perfect control of which characters remain, remember that the best way to manage this issue is to delete characters yourself before the merge to reduce the number of characters for the new server to seven or less. Please note that any items owned by deleted characters will be unrecoverable, so make sure you know which characters you're keeping and plan accordingly.
3. Character Name Conflicts Resolved
Once a character has successfully passed the above steps, it is placed on the destination server. If your character has the same name as other characters on the new server, each character with that name will have a number appended to its character name. These numbers correlate to the server a character originated from. You will notice this name change after logging in to the Character Selection screen. Review the "Name Changes After the Server Merge" section below for the process to change a character name that had a name conflict.
Server Merge Special Cases
Characters on a Low-Level Subclass
The server merge process only examines the main class of each character. If you have a high-level main character that is on a low-level subclass at the time of the merge, only the character's main class level is taken into account.
Example: You have seven high level (76+) characters and one level 50 character among the merging servers, each on their main class. You switch one of the high-level characters to its level 40 subclass. Now it appears that you have six level 76+ characters, one level 50 character, and one level 40 character. When the server merge occurs, the level 50 character will be deleted because its main class was the lowest of all eight characters. The level 40 subclass character will remain.
Name Changes After the Server Merge
If your character's name has been changed in the server merge due to a name conflict, you will have to change its name before entering the game. Successfully keeping an original name is still technically a name change because by doing so you will be getting rid of the number that was appended to the name to resolve the name conflict during the merge. Name conflicts are basically resolved by giving the desired name to the first player that requests it, but there are certain conditions. If multiple parties have the same name pre-merge whoever logs in will be able to first claim the name. However, if the other parties would like to also have a fair chance for the name as well, they can request the support team to investigate the character history on each party's respective server.
To keep or change your character name:
As you log in after the server merge, in the character selection screen, you may see that a character has a new number at the end of its name. This means that your character had a character name conflict. If you don't have a new number at the end of your character's name, you can log straight in to the game.
When you select a character that has a name conflict, a message box pops up explaining that there was a character name conflict. It says: "Please enter your desired name."
You can enter in your original character name. Entering your original character name lets you check to see if the name is still available.
If a character has already claimed the name that you are trying to assign to your character, you will not be able to use that name.
You will see the above popup message box. Enter a different character name in the message box. Repeat this process until you have successfully renamed your character. You can now log in with that new name.
There will be an appeals process for those players who lose a name due to griefing or name-stealing tactics. If you lose a name due to griefing, send a support ticket and we will investigate the issue. If you lose a name and you're not sure if it was through griefing or if it was a legitimate name-claim, send a support ticket so that we can investigate for you.
Clans
These are the general clan rules after the server merge:
All alliances will be disbanded.
The in-game clan community board will be reset.
The clan crest will be reset.
All clan wars will be ended as a tie.
Remove items from clan warehouses. Only Adena will be transferred with the clan warehouse.
The following clan information will be transferred intact:
Reputation points
Clan skills
Clan level
Clan rights
Clan leadership and ranks
Clan Name Conflicts
A clan name conflict is dealt with similar to a character name conflict. Each clan that shared the same name will find that its clan name now has a number appended to its clan name. These numbers correlate to the server a clan name originated from. Clan name conflicts are resolved by giving the desired name to the first clan that requests it.
To resolve a clan name conflict:
Speak to a High Priest NPC in any town and select Clan from the chat list.
In the Clan list, select Change Clan Name.
You will see a popup message box that explains that your clan was among those with duplicate clan names, and you should change your clan's name.
You can enter your original clan name. Entering your original clan name lets you check to see if the name is still available
If your clan name request works, you will see a system message in your regular chat window that says: "A clan name change application has been submitted."
If your requested clan name has already been claimed by another clan, you will see a message explaining that the name already exists and requiring you to pick another one. Enter a different clan name in the message box. Repeat this process until you have successfully requested a new clan name.
Once you have successfully submitted a clan name change request, note that the change takes effect after the next server maintenance period.
Castles, Manors, and Clan Halls
All Castles, Clan Halls, and Fortresses will be reset.
Clans who own auctionable, contestable, or provisional clan halls will be compensated with Clan Fame and Adena. This will be available after the servers come back up from maintenance.
For auctionable Clan Halls, the winning bid amount will be sent to the Clan Warehouse.
Clans will be compensated for Clan Hall rent based on the amount initially paid and time remaining on the rent before the merge.
Clan Fame will be provided to the Clan that owns any contestable Castles or Clan Halls on the day of the server merge.
Clan Hall Auctions will not stop, however only auctions won before the announcement will be given compensation.
The Dimensional Castle Siege owners for Shilen, Magmeld, and Bartz will be reset during the merge. We will be upgrading those clans' Dimensional Energy item and sending it to them a week before the first dimensional castle siege for the Freya server.
Olympiad
Olympiad and Ceremony of Chaos will begin on May 1, 2016.
Olympiad Points will be reset
Olympiad Tokens will transfer
Hero characters and weapons will be reset
The Clan of the 1st place character as of April 13th, 2016 in Ceremony of Chaos will receive 5000 fame.