changing the connection string in SQL Server

After SSIS package deployed to new environment still it may use old connection string.

how to change the connection string i.e initial catalog or server name parameter from Agent job > configuration > connection manger .Is there a possibility to do from here ?

Yes, It's possible when you are sysadmin and you can change manually by following:

Right click on AgentJob -> Properties -> Job step -> Configuration -> Connection Managers

Below Connection Managers -> select Name of database then on properties ->

• Connectionstring -> Data Source=yourServerName;InitialCatalog=Databasename;Provider=SQLNCLI11.1;IntegratedSecurity = SSPI;Auto Translate=False; (you can edit Data source and intial catalog manually)

and

• Servername = 'yourservername'