1. Enter a name and base path for the REST service module. The following code example provides teller and transfers as values. Replace these values with information that is specific to your environment.

   DECLARE
       //Provide a name for the REST service module
       restModuleName VARCHAR2(256):= 'teller'; 
       //Provide a base path for the REST service
       restModuleBasePath VARCHAR2(256):= 'transfers';

2. Define a module, and then define a template for the module.

   
   BEGIN
       ORDS.define_module(
               p_module_name    => restModuleName,
               p_base_path      => restModuleBasePath,
               p_items_per_page => 0);
    
       ORDS.define_template(
               p_module_name    => restModuleName,
               p_pattern        => 'transfer');

3. Provide source code for the module. The following code snippet demonstrates how you can define transaction boundaries by using the MicroTx PL/SQL library functions, tmm_begin_tx(), tmm_rollback_tx(), and tmm_commit_tx(). When you begin a transaction, it returns a MicroTxTransaction object. You will use this returned object to commit or roll back the global transaction. For reference information about the PL/SQL functions, see MicroTx PL/SQL Library Functions.

   
   ORDS.define_handler(
       p_module_name    => restModuleName,
       p_pattern        => 'transfer',
       p_method         => 'POST',
       p_source_type    => ORDS.source_type_plsql,
       p_source         => '
           DECLARE
           payload      JSON_OBJECT_T;
           l_from_account VARCHAR2(32);
           l_to_account VARCHAR2(32);
           l_amount VARCHAR2(32);
           l_microTxTransaction MicroTxTransaction;
           l_forwardHeaders ForwardHeaders;
           l_is_withdraw_successful BOOLEAN;
           l_is_deposit_successful BOOLEAN;
           BEGIN
               payload := JSON_OBJECT_T(:body);
               l_from_account := payload.get_String(''from'');
               l_to_account := payload.get_String(''to'');
               l_amount := payload.get_String(''amount'');
   
               -- Set response header
               OWA_UTIL.mime_header(''application/json'', FALSE);
               OWA_UTIL.http_header_close;
   
               -- set forward headers
               -- the bind variables are case sensitive
               l_forwardHeaders := ForwardHeaders(:authorization, :tmmTxToken, :requestId);
   
               -- tmm_begin_tx starts a global transaction that spans across multiple microservices.
               -- It returns a MicroTxTransaction object which has the transaction metadata.
               -- 60000 is the time, in milliseconds, for which the transaction remains active. 
               -- If a transaction is not committed or rolled back within the specified time period, the transaction is rolled back.
               l_microTxTransaction := tmm_begin_tx(l_forwardHeaders, 60000);
   
               l_is_withdraw_successful := callWithdrawParticipant(l_from_account, l_amount, l_microTxTransaction , l_forwardHeaders);
               IF NOT l_is_withdraw_successful THEN
                   tmm_rollback_tx(l_microTxTransaction, l_forwardHeaders);
                   :status_code := 500;
                   HTP.p(''{"error" : "Withdraw failed"}'');
                   RETURN;
               END IF;
   
               l_is_deposit_successful := callDepositParticipant(l_to_account, l_amount, l_microTxTransaction, l_forwardHeaders);
               IF NOT l_is_deposit_successful THEN
                   tmm_rollback_tx(l_microTxTransaction, l_forwardHeaders);
                   :status_code := 500;
                   HTP.p(''{"error" : "Deposit failed"}'');
                   RETURN;
               END IF;
   
               -- Within global transaction
               creditFundTransferRewards(l_from_account, l_amount);
   
               tmm_commit_tx(l_microTxTransaction, l_forwardHeaders);
               :status_code := 200;
               HTP.P(''{"message":"Transfer successful"}'');
               END;',
           p_items_per_page => 0);

All the external calls and DML statements that an initiator application runs after calling tmm_begin_tx() and before calling tmm_commit_tx() is considered as part of a single global transaction. In case tmm_rollback_tx() is called, it rolls back all external calls and DML statements that are executed after the application calls tmm_begin_tx() and before the application calls tmm_commit_tx().

-- Specify the name for the link header
p_name_01 => 'Link',
p_value_01 => getTmmLinkHeader(l_microTxTransaction),

Where, l_microTxTransaction is the MicroTxTransaction object that the TMM_BEGIN_TX function returns. This object contains the transaction metadata.