Messages are not synced on imac and macbook -- missing a month of messages

Question

I have used Messages on an iMac at home, and a Macbook Pro on travel, both of them using OS 10.8.4.  The Messages/Preferences/Acclounts window shows that both computers are using the same settings. During travel last month I added several Messages accounts, using the Macbook. These do not now show up on the iMac. The imac shows 4 of these accounts, and when I now put a message on one of these, with either mac, it shows up on both macs just fine. But I am missing a month of messages that were sent on the macbook that do not show up on the imac, and I have 5 accounts that were added to the macbook Messages that do not appear on the imac Messages. How can I sync everything?

Answer 1

HI,
This is a pic of my Window Menu in drop down and the Preferences opened at the Accounts pane.
I have highlighted the most well known Account of my AIM Screen Name.
As you can see the list here on the left has a Scroll Bar and I am not displaying all the 10 Accounts shown in the in the Window Menu.
The Window Menu will show them as a combined list by default, due to the setting in the General Pane of the Preferences.
The Messages Menu itself > Accounts will also show the number of Accounts that are Logged in
By Default (without you ever having started up Messages) it will two accounts.
These will be the iMessages account (Minus any Apple ID) and the Bonjour account that is normally Disabled by default (it is only any use when two or more Macs are on the same LAN and have the Bonjour Account Enabled).
If I untick the "Enable this Account" Box for some of the accounts I can get down to 3 Buddy List type accounts listed in the Window Menu and the Main Messages Window.
You may notice from the first pic that the Description field in the Preferences (Main AIM) is the name in the list in the Window Menu and at the bottom left in the Main Messages window.
Sync
In terms of iMessages this means "Display on all Devices".
It does not mean mark as read on all devices or deal with as if dealt with on another device.
iMessages and Chats that might be Saved.
The application will Save Chats and iMessages if set to do so in the Messages Pane of the Preferences.
It will do so when you close the app. If you leave a conversation (iMessages) or a Chat (Instant Messages from Buddies) on display in the Main Messages window over a number of days it is likely that Messages will create a Save of this each day in ~/Library/Messages/Archive/(by date)
Also in this ~/Library/Messages folder is the Chat.db items
This is the bit that hold a running record of the iMessages conversations you have had and tends to be the bit that brings up the "History" if you restart a conversation with a Contact you have already iMessage'd.
Moving corresponding chat.db items from one computer to another may need the Ownership changed.
Go to the ~/Library/Messages folder.
Highlight the chat.db item and then do a Get Info (CMD and i keys together).
This brings up the Info Panel and at the bottom are the Read and Write Privileges
Highlighting th top "person" and then using the Cogwheel type icon should reveal your Shortname in greyed out text if you Own the item.
As I own mine my shortname is greyed out
Of course, using my shortname as an example you may be "ralph" on both computers but you  may need to make the Moved file "yours" on this computer.
I only have one Mountain Lion compatible computer and have not tried this to see that it actually works in "moving" chats from one computer to another.
8:45 PM      Thursday; August 1, 2013
  iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.4)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously