UCCHECK ERRORS SOLUTION DURING UPGRADE
As of 6.10 releases, SAP has introduced Unicode; a form of encoding that complies with ISO/IEC 10646 and covers all languages. Each character is generally mapped using 16 bits (=2 bytes) and this offers a maximum of 65536 bit combinations. UNICODE
UCCHECK
To identify all the objects which need an ABAP adjustment following the Unicode Migration, SAP has provided a standard transaction called UCCHECK. UCHECK utility identifies the objects that require Unicode Migration and lists down the exact Unicode adjustment that needs to be made for those objects. The developer then needs to make the adjustment to the listed objects based on the documentation provided by the SAP.UCHECK Utility
To start the UCCHECK utility, just run the transaction ‘UCCHECK’. The following selection screen would come up.

In Object name field, enter the objects for which you want to check Unicode compatibility. You can directly upload the objects from an Excel file.
Change the max number of programs field so that it is high enough to return all your potential problems.
Once the transaction as finished analysing your system it will provide you with a report detailing all your objects which do not currently have the unicode attribute selected. It also details what problems you will have when you check the unicode attribute and try to reactivate the object.
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Green Traffic symbol: Unicode attribute can be turned on without any modification to the object.
Red Traffic symbol: Modification(s) to the object will be required before unicode can be switched on
Yellow Traffic Symbol : Error in code which is unrelated to unicode conversion
The UCCHECK result would form the basis of estimation since it will give the exact number of objects would need syntactical adjustment for Unicode.
SETTING THE UNICODE ATTRIBUTE
For an ABAP program to run under Unicode, one must have installed a Unicode-enabled SAP System, connected to a suitable operating system and database. A Unicode-compatible ABAP program is one where all Unicode checks are in effect. Such program returns the same result in Unicode system as in non-Unicode system (in most cases).
Setting the Unicode attribute for all the ABAP programs is a MUST before the Unicode Migration of the database takes place. In case the attribute is not set, the program will not get activated/executed in Unicode environment even though all the syntaxes in the program may comply with Unicode standards.
How to set the Unicode Attribute
The Unicode Attribute flag for the custom objects can be set in 2 ways
Using UCCHECK Tool
The UCCHECK tool would set the Unicode Attribute flag for only those objects which appear in the green light in the UCCHECK output.Advantage:
Note:
To set the Unicode attribute using UCCHECK, select all the objects in green light in the UCCHECK output and then click on the "Set Unicode Attribute" button as shown below.

Manual Method
In this method, the developer has to explicitly go to the program attributes and set the flag as shown below. Go directly to the object,
Go To ->Attributes->Change Display->Check the Unicode Flag Active-> Save->Activate.
It is advisable that the changes for setting the Unicode Attribute flag for the custom programs be captured in a single transport.
COMMON ERRORS FOUND IN THE UCCHECK AND THEIR SOLUTIONS
I have put a WIKI "UNICODE ERROR SOLUTION" in which I've discussed most common errors and their solution. The link to the wiki is:
http://www.sdn.sap.com/irj/scn/wiki?path=/display/si/unicode+errors+solution
Kindly go through it and Update your comments and your knowledge in that list.