Access Alchemy 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 Alchemy to create a database link from Alchemy to Oracle and to query Alchemy data through the SQL*Plus tool. You can also create the database link and execute queries from SQL Developer.

Connect to Alchemy as an ODBC Data Source

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

Start by setting the Profile connection property to the location of the Alchemy Profile on disk (e.g. C:\profiles\Alchemy.apip). Next, set the ProfileSettings connection property to the connection string for Alchemy (see below).

Alchemy API Profile Settings

Alchemy uses API key authentication. The API key is supplied in the request URL path. To obtain an API key:

1. Sign in to your Alchemy account at https://dashboard.alchemy.com.
2. Open an existing app or create a new one.
3. Copy the app's API key from the API Key dialog.

After obtaining your API key, set the following connection properties:

• AuthScheme: Set this to APIKey.
• Network: Optional. The blockchain network slug for NFT API requests (for example, eth-mainnet, base-mainnet, polygon-mainnet). Defaults to eth-mainnet.

Set the following in the ProfileSettings connection property:

• APIKey: Set this to your Alchemy app API key.

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 Alchemy 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 Alchemy 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 API Source]
Driver = CData ODBC Driver for Alchemy
Description = My Description
Profile = C:\profiles\Alchemy.apip
AuthScheme = APIKey
Network = eth-mainnet
ProfileSettings = 'APIKey = your_api_key'

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 Alchemy data just as you would an Oracle database. Set the following properties when working with Alchemy 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-api/lib/cdata.odbc.api.ini in a text editor and set the encoding.

cdata.odbc.api.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 Alchemy data that enables you to query live Alchemy data as an Oracle database.

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

   initmyalchemydb.ora

   HS_FDS_CONNECT_INFO = "CData API 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 = myalchemydb)
         (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 = myalchemydb)
         (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

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

4. Restart the listener.

5. Test the configuration with the following command:

   tnsping myalchemydb

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

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

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

SELECT * from "ContractsForOwner"@myalchemydb WHERE Owner = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045';