%d is the maximum allowable size of an index. Composite index specified is %d bytes.
This error occurs when the sum of the lengths of the columns that make up the composite index exceeds 256 bytes.
A composite index is an index that uses from 2 to 16 columns. For example, the following shows a composite index using objects from the pubs database:
create index idxPubNameCity ON publishers (pub_name, city) go
In this example, pub_name is defined as varchar(40) and city as varchar(20). Each character requires 1 byte of storage, so the total length of this composite index is 60 bytes. Note that when using varchar columns, the index will assume the maximum length of the varchar column to calculate the length of the composite index.
Examine the lengths of the columns in your composite index and make sure that the total does not exceed 256 bytes. For information on determining the storage size for different Microsoft SQL Server datatypes, see the Microsoft SQL Server Transact-SQL Reference. For more information on indexes, see the Microsoft SQL Server Database Developer's Companion and the CREATE INDEX statement in the Microsoft SQL Server Transact-SQL Reference.