Access Linear Data as a Remote Oracle Database

The Oracle Database Gateway for ODBC and Heterogeneous Services technology enable you to connect to ODBC data sources as remote Oracle databases. This article shows how to use the CData ODBC Driver for Linear to create a database link from Linear to Oracle and to query Linear data through the SQL*Plus tool. You can also create the database link and execute queries from SQL Developer.

Connect to Linear as an ODBC Data Source

Information for connecting to Linear follows, along with different instructions for configuring a DSN in Windows and Linux environments.

You can authenticate to Linear with a personal API key or with OAuth 2.0. The API key is the simplest option for connecting with your own Linear account.

Authenticating with an API Key

Set the following connection properties:

• AuthScheme: Set this to APIKey.
• APIKey: A Linear personal API key.

To create a personal API key, log in to Linear, open Settings > Security & access > Personal API keys, select New API key, and create it. Copy the key immediately, because Linear shows it only once.

Authenticating with OAuth

OAuth requires a custom OAuth application registered in Linear (Settings > API > OAuth applications), which provides the OAuthClientId and OAuthClientSecret. Two flows are supported:

• Authorization code: Set AuthScheme to OAuth, InitiateOAuth to GETANDREFRESH, and provide OAuthClientId, OAuthClientSecret, and the CallbackURL defined in your application (e.g., http://localhost:33333). The driver opens Linear in your browser so you can grant access.
• Client credentials: Set AuthScheme to OAuthClient and provide OAuthClientId and OAuthClientSecret. This authenticates the application itself, with no browser interaction, and suits machine-to-machine integrations.

By default, the driver requests the read,write scopes. The driver refreshes the access token automatically when it expires.

Windows

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

Note: If you need to modify the DSN or create other Linear DSNs, you must use a system DSN and the bitness of the DSN must match your Oracle system. You can access and create 32-bit DSNs on a 64-bit system by opening the 32-bit ODBC Data Source Administrator from C:\Windows\SysWOW64\odbcad32.exe.

Linux

If you are installing the CData ODBC Driver for Linear in a Linux environment, the driver installation predefines a system DSN. You can modify the DSN by editing the system data sources file (/etc/odbc.ini) and defining the required connection properties.

/etc/odbc.ini

[CData Linear Source]
Driver = CData ODBC Driver for Linear
Description = My Description
AuthScheme = APIKey
APIKey = myAPIKey

For specific information on using these configuration files, please refer to the help documentation (installed and found online).

Set Connection Properties for Compatibility with Oracle

The driver provides several connection properties that streamline accessing Linear data just as you would an Oracle database. Set the following properties when working with Linear data in SQL*Plus and SQL Developer. For compatibility with Oracle, you will need to set the following connection properties, in addition to authentication and other required connection properties.

• MapToWVarchar=False

  Set this property to map string data types to SQL_VARCHAR instead of SQL_WVARCHAR. By default, the driver uses SQL_WVARCHAR to accommodate various international character sets. You can use this property to avoid the ORA-28528 Heterogeneous Services data type conversion error when the Unicode type is returned.

• MaximumColumnSize=4000

  Set this property to restrict the maximum column size to 4000 characters.

• IncludeDualTable=True

  Set this property to mock the Oracle DUAL table. SQL Developer uses this table to test the connection.

Linux Configuration

In Linux environments, Oracle uses UTF-8 to communicate with the unixODBC Driver manager, whereas the default driver encoding is UTF-16. To resolve this, open the file /opt/cdata/cdata-driver-for-linear/lib/cdata.odbc.linear.ini in a text editor and set the encoding.

cdata.odbc.linear.ini

[Driver]
DriverManagerEncoding = UTF-8

Configure the ODBC Gateway, Oracle Net, and Oracle Database

Follow the procedure below to set up an ODBC gateway to Linear data that enables you to query live Linear data as an Oracle database.

1. Create the file initmylineardb.ora in the folder oracle-home-directory/hs/admin and add the following setting:

   initmylineardb.ora

   HS_FDS_CONNECT_INFO = "CData Linear Sys"

2. Add an entry to the listener.ora file. This file is located in oracle-home-directory/NETWORK/admin.

   If you are using the Database Gateway for ODBC, your listener.ora needs to have a SID_LIST_LISTENER entry that resembles the following:

   listener.ora

   
   SID_LIST_LISTENER =
     (SID_LIST =
       (SID_DESC =
         (SID_NAME = mylineardb)
         (ORACLE_HOME = your-oracle-home)
         (PROGRAM = dg4odbc)
       )
     )
   

   If you are using Heterogeneous Services, your listener.ora needs to have a SID_LIST_LISTENER entry that resembles the following:

   listener.ora

   
   SID_LIST_LISTENER =
     (SID_LIST =
       (SID_DESC =
         (SID_NAME = mylineardb)
         (ORACLE_HOME = your-oracle-home)
         (PROGRAM = hsodbc)
       )
     )
   

3. Add the connect descriptor below in tnsnames.ora, located in oracle-home-directory/NETWORK/admin:

   tnsnames.ora

   
   mylineardb  =
     (DESCRIPTION=
       (ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=1521))
       (CONNECT_DATA=(SID=mylineardb))
       (HS=OK)
     ) 
   

4. Restart the listener.

5. Test the configuration with the following command:

   tnsping mylineardb

6. Open SQL*Plus and create the database link with the command below:

   CREATE DATABASE LINK mylineardb CONNECT TO "user" IDENTIFIED BY "password" USING 'mylineardb';

You can now execute queries in SQL*Plus like the one below (note the double quotation marks around the table name):

SELECT * from "Team"@mylineardb WHERE key = 'ENG';