Matching the schema of a SQL Server DB to an Oracle DB - sql-server

Question

Are there known products that can perform schema matching on any level between SQL Server and Oracle as described here? If not a product, would there be a documented methodology on how to perform maybe some semantic search and comparison of db tables, fields, and even data?
I have an existing SQL Server database which currently experiences a lot of trouble updating its data as it uses a lot of undocumented and unreadable legacy code to extract information from various external data sources. Fortunately, there exists an Oracle database that, based on the nature of the business, seems to contain all the information required by the SQL Server DB. The problem is, the schemas between the two environments are vastly different. They don't follow a common naming convention, and may not even follow the same normalization (some tables may be flat on one and normalized on the other).
The naive approach of trying to go through each table and column in SQL Server and then manually and visually searching for possible matches on the Oracle one seems quite impractical, given that there are hundreds of tables between the two databases.

Answer 1

There are commercial solutions(i.e. Database Compare Suite, Cross Database Studio) in the market which can be used to compare both homogeneous and heterogeneous database environments. But it's not good idea to spent money for those tools only for the schema comparison.
There might be several methods/tools/solutions which has certain limitations based on their scope. I am giving solution to compare schema matching between SQL Server and Oracle. Level of matching like table contents and data structure depends on your level of implementation.
In my Approach, suggesting following steps to full fill your requirements:
Establish SQL Server link server to Oracle Database. Steps are mentioned in the reply trail.
Now, access SQL Server and Oracle tables directly from SQL Server environment itself. It's feasible to compare table data using following approach:
SQL Server :
select field1, field2, field_N from openquery(DEV, 'select * from oracle_owner_schema.testtable')
minus
select field1, field2, field_N from sqlserver_database.schema_name.testtable
3 You can compare data structure(field length, data type, default value, etc.) by using dictionary table from SQL Server and Oracle in a same way.
Establish SQL Server link server to Oracle Database
Setup ODAC
Copy missing DLLs from instaclient to c:\oracle\product...\client_1\BIN [Location in which ODAC was installed.]
Add hostname, portnumber, and service name in c:\oracle\product...\client_1\network\admin\tnsnames.ora, sample:
LOCALSERVER =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = IP_Hostname_Oracle_Server)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = orcl)
)
)
Configuration in the SQL Server:
a. Connect to SQL server
b. Database>Server Objects>link servers>providers>OraOLEDB.Oracle>Right
c. Click>Properties>"Check Enable for 'Allow Inprocess'", then Save it.
d. Database>Server Objects>link servers>Right Click>New Link Server>
**************General TAB*************************
Linked server: Any Name for link server in MSSQL
Provide name: Oracle Provider
Product Name: Oracle
Datasource: Provide name which you have added in tnsnames.ora
****************Security TAB***************************
Choose "Be made using this security contest:"
Remote login: username for remote database <<e.g. guest >>
With password: password <<e.g. guest>>
How to use:
select * from openquery(Linked_server_Name, 'select * from schema_name.table_name');
i.e. select * from openquery(Any Name_for_link_server_in_MSSQL, 'select * from oracle_owner_schema.testtable');
Note: Version of ODAC and oracle client should be same.