Hi Venkatesh
I think you have to upgrade the MS Sql 2012 R2. Kindly follow the steps:
1. Current ECC system NW 7.00 SP 23 to Minimum sp level 28, along with MS SQl latest service pack.
2. Upgrade the existing MS SQL 2008 R2 to 2012 R2. refer the SAP Note 1676665 - Setting up Microsoft SQL Server 2012
3. Upgrade the ECC system to NW 7.4
BR
SS