10 Gateway Configuration Using TCP/IP Communication Protocol

10.1 Before You Begin

This chapter requires you to input parameters unique to your system in order to properly configure the gateway and TCP/IP communications interface.

Refer to Appendix E, "Configuration Worksheet" for a worksheet listing the installation parameters you will need to know before you can complete the configuration process. Ask your network administrator to provide you with these unique parameter names before you begin.

10.2 Preparing to Configure a Gateway Installation/Upgrade

There are three ways to establish the gateway-Oracle Integrating Server relationship when you are installing or upgrading/migrating the gateway:

• When the Oracle Integrating Server and the gateway are installed in the same ORACLE_HOME on the same machine;

• When the Oracle Integrating Server and the gateway are installed on separate machine; or

• When the Oracle Integrating Server and the gateway are on the same machine but in different directories

Depending on the location of your gateway and your Oracle Integrating Server, you may need to transfer some of the gateway administrative files to the location where the Oracle Integrating Server is installed.

Follow the instructions suitable to your combination of the gateway-Oracle Integrating Server locations listed below.

When the Oracle Integrating Server and the gateway are installed in the same ORACLE_HOME on the same machine

You do not need to transfer files. Proceed to "Configuring the Oracle Integrating Server: First Time Installation".

When the Oracle Integrating Server and the gateway are installed on separate machine

1. Locate the gateway administrative files in the gateway %ORACLE_HOME%\pg4appc\admin directory. All files in this directory that have the suffix .sql, .pkh, and .pkb must be copied into a similarly-named directory in the Oracle Integrating Server's Oracle home directory.

2. Now locate the gateway demo files and subdirectories in the gateway %ORACLE_HOME%\pg4appc\demo directory. Copy the pgavsn.sql and pgaecho.sql files into a similarly named directory in the Oracle Integrating Server.

3. Copy the pgaims.sql file from the gateway Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory to your Oracle Integrating Server's Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory.

4. Optional Steps: If you want to run IVTNV and IVTNO, then you will need to copy the ivtno.ctl, ivtnod.sql, ivtnv.ctl, and ivtnvd.sql files into the Oracle Integrating Server's Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory as well. Make sure to generate the required TIPs and transfer them as well.

When the Oracle Integrating Server and the gateway are on the same machine but in different directories

You must change your gateway's Oracle home to the Oracle Integrating Server's Oracle home directory.

1. For example, if your gateway's Oracle home is set as follows:

   C:\> echo %ORACLE_HOME%
   C:\oracle\pga\10.2
   
   

   and your server's Oracle home is located in the '\oracle\pga\10.2' directory, then you need to do the following:

   C:\> SET ORACLE_HOME=C:\oracle\pga\10.2
   
   

2. Now, create the directories with the following commands:

   C:\> cd %ORACLE_HOME%
   C:\> mkdir pg4appc
   C:\> mkdir pg4appc\admin
   C:\> mkdir pg4appc\demo
   C:\> mkdir pg4appc\demo\IMS
   
   

3. Use whatever file transfer mechanism is available on your system to copy all the .sql, .pkh, and .pkb files from the gateway's Oracle home %ORACLE_HOME%\pg4appc\admin directory to the Oracle Integrating Server's Oracle home %ORACLE_HOME%\pg4appc\admin directory.

4. You may also transfer the demo files from the gateway directory to the Oracle Integrating Server directory. Copy the pgavsn.sql and pgaecho.sql files and directory recursively from the gateway Oracle home's %ORACLE_HOME%\pg4appc\demo directory to the Oracle Integrating Server's %ORACLE_HOME%\pg4appc\demo directory.

5. You may also copy the pgaims.sql file from the gateway Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory to the Oracle Integrating Server Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory.

   Optional Steps: If you want to run IVTNV and IVTNO, then you will need to copy the ivtno.ctl, ivtnod.sql, ivtnv.ctl, and ivtnvd.sql files into the Oracle Integrating Server's Oracle home %ORACLE_HOME%\pg4appc\demo\IMS directory as well. Make sure to generate the required TIPs and transfer them as well.

Proceed to "Configuring the Oracle Integrating Server: First Time Installation". Following those steps, you may want to perform the Optional Configuration Steps to Permit Multiple Users,.

10.3 Configuring the Oracle Integrating Server: First Time Installation

Follow these steps to configure the Oracle Integrating Server after installing the Oracle Procedural Gateway for APPC.

1. Ensure that the UTL_RAW PL/SQL package has been installed on the Oracle Integrating Server. All PGAU-generated TIP specifications use UTL_RAW, which provides routines for manipulating raw data.

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user SYS.

   2. From SQL*Plus, enter the following command:

      SQL> DESCRIBE UTL_RAW
      
      

      The DESCRIBE statement produces output on the screen. If you browse through the output, then you should see some functions, including a compare function. If you do not see this output, then continue the UTL_RAW installation by performing Step d.

      If the DESCRIBE statement indicates success, then your Oracle Integrating Server has UTL_RAW installed and you can proceed to Step 2.

   3. Use SQL*Plus to connect to the Oracle Integrating Server as SYS.

   4. From SQL*Plus, run the utlraw.sql and prvtrawb.plb scripts in the Oracle Integrating Server %ORACLE_HOME%\rdbms\admin directory, in the following order:

      C:\> cd %ORACLE_HOME%\rdbms\admin
      SQL> @utlraw.sql
      SQL> @prvtrawb.sql
      
      

2. Ensure that the DBMS_OUTPUT standard PL/SQL package is enabled on your Oracle Integrating Server. The sample programs and installation verification programs on the distribution media use this standard package.

   1. If necessary, then use SQL*Plus to connect to the Oracle Integrating Server as user SYS.

   2. Enter the following command:

      SQL> DESCRIBE DBMS_OUTPUT
      
      

      The DESCRIBE statement produces output on your screen. If you browse through that output, then you should see some functions, including a put_line function.

      If you do not see this output, then you must create the DBMS_OUTPUT package. Refer to the Oracle Database Application Developer's Guide for more information about creating the DBMS_OUTPUT package. After successful installation of the DBMS_OUTPUT package, issue the DESCRIBE statement.

      If the DESCRIBE statement indicates success, then your Oracle Integrating Server has DBMS_OUTPUT created, and you can proceed to Step 3.

3. Install the UTL_PG PL/SQL package. All PGAU-generated TIP specifications use UTL_PG, which provides routines for performing numeric conversions to and from raw data.

   1. If necessary, then use SQL*Plus to connect to the Oracle Integrating Server as user SYS.

   2. From SQL*Plus, run the utlpg.sql and prvtpgb.plb scripts in the Oracle Integrating Server's %ORACLE_HOME%\rdbms\admin directory, in the following order:

      C:\> cd %ORACLE_HOME%\rdbms\admin
      SQL> @utlpg.sql
      SQL> @prvtpgb.plb
      
      

4. Install the Heterogeneous Services (HS) catalogs.

   1. If necessary, then use SQL*Plus to connect to the Oracle Integrating Server as user SYS.

   2. Enter the following command:

      SQL> DESCRIBE HS_FDS_CLASS
      
      

      The DESCRIBE statement produces output on the screen. If the DESCRIBE statement indicates success, then Heterogeneous Services catalogs have been created on your Oracle Integrating Server and you can proceed to Step 5.

      If the DESCRIBE statement does not indicate success, then you must create Heterogeneous Services catalogs and you must perform Step c below:

   3. If it is necessary to create the Heterogeneous Services catalog, then enter the following command:

      C:\> cd %ORACLE_HOME%\rdbms\admin
      SQL> @caths.sql
      
      

5. Create a public database link to access the Oracle Procedural Gateway for APPC:

   Use SQL*Plus to connect to the Oracle Integrating Server as user SYSTEM. You can use the following SQL*Plus sample whether the Oracle Integrating Server and the gateway are on the same system or on different systems. In the following sample, pgasrv is the tns_name_entry that will be assigned to the gateway when you modify the tnsnames.ora file later in this chapter.

   SQL> CREATE PUBLIC DATABASE LINK PGA USING 'PGASRV'
   
   

6. Create the gateway administrator user PGAADMIN and install the PG DD.

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user SYSTEM.

   2. From SQL*Plus, run the pgacr8au.sql script in the %ORACLE_HOME%\pg4appc\admin directory. This script creates the PGAADMIN user ID.

      The initial password defined for PGAADMIN is PGAADMIN. Use the ALTER USER command to change the password. For further information about password issues, refer to the Oracle Database SQL Reference.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgacr8au.sql
      
      

   3. Use SQL*Plus to connect to the Oracle Integrating Server as user PGAADMIN.

   4. From SQL*Plus, run the pgddcr8.sql script in the %ORACLE_HOME%\pg4appc\admin directory. This script installs the PG DD.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgddcr8.sql
      
      

   5. From SQL*Plus, connect to the Oracle Integrating Server as user SYS.

   6. Grant execution privileges on DBMS_PIPE to PGAADMIN:

      SQL> GRANT EXECUTE ON DBMS_PIPE TO PGAADMIN
      
      

7. Ensure that the pg4tcpmap package has been installed on your Oracle Integrating Server. Follow Steps a through c to test for proper installation of pg4tcpmap.

   Refer to "Output for the pg4tcpmap Tool" in Appendix B for a sample of the output from the pg4tcpmap tool, and refer to Chapter 6 of the Oracle Procedural Gateway for APPC User's Guide for details about the commands needed to run the tool.

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user SYSTEM.

   2. Enter the following command:

      SQL> select table_name, owner
      from dba_tables
      where table_name = 'PGA_TCP_IMSC', 
      and owner = 'PGAADMIN';
      SQL> column owner format a 10
      SQL> column index_name format a 18
      SQL> column table_name format a 14
      SQL> select owner, index_name, table_name, uniqueness
      from dba_indexes
      where index_name = 'PGA_TCP_IMSC_IND';
      
      

      Both SELECT statements must produce one row each. Following is the result for the first select statement:

      TABLE_NAME                        OWNER
      ------------------------------  ------------------------------
      PGA_TCP_IMSC                      PGAADMIN
      

      Following is the result of the second select statement:

      OWNER          INDEX_NAME           TABLE_NAME      UNIQUENESS
      ----------     ------------------   --------------  ---------
      PGAADMIN       PGA_TCP_IMSC_IND     PGA_TCP_IMSC    UNIQUE
      
      

      If the select statements produce the preceeding output on the screen, then you can skip Step C. If the select statement produces no output or more than one row, then the result is not the same as the output described above, and it is necessary for you to perform Step c.

   3. From SQL*Plus, run the pgaimsc.sql script in the Oracle Integrating Server's %ORACLE_HOME%\pg4appc\admin directory:

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgaimsc.sql
      
      

8. Install the TIP trace access PL/SQL routines. These routines require that the DBMS_PIPES standard PL/SQL package is installed and that PGAADMIN has execute privileges on it. For more information about DBMS_PIPES, refer to the Oracle Database Application Developer's Guide.

   1. If necessary, then use SQL*Plus to connect to the Oracle Integrating Server as user PGAADMIN.

   2. From SQL*Plus, run the pgatiptr.sql script in the %ORACLE_HOME%\pg4appc\admin directory. This script creates PL/SQL routines that can be called to read and purge trace information created by PGAU-generated TIP specifications. It also creates public synonyms for these routines. The script prompts you for the necessary user IDs and passwords.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgatiptr.sql
      
      

9. Install the GPGLOCAL package. This package is required for compilation and execution of all PGAU-generated TIP specifications. TIP developers should be granted execute privileges on GPGLOCAL (refer to "Optional Configuration Steps to Permit Multiple Users").

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user PGAADMIN.

   2. From SQL*Plus, run the gpglocal.pkh script in the %ORACLE_HOME%\pg4appc\admin directory. This script compiles the GPGLOCAL package specification.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @gpglocal.pkh
      
      

   3. From SQL*Plus, run the gpglocal.pkb script in the %ORACLE_HOME%\pg4appc\admin directory. This script compiles the GPGLOCAL package body.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @gpglocal.pkb
      
      

      Note:

      Recompile TIPs when changing communication protocol from SNA to TCP/IP:

      If you have existing TIPs that were generated previously on a gateway using the SNA protocol and you want to use the new TCP/IP feature, then the TIPs will have to be regenerated by PGAU with mandatory NLS_LANGUAGE and Side Profile Settings. Specify the suitable ASCII character set in the DEFINE TRANSACTION command.

      This is due to the fact that the gateway assumes that the appropriate user exit in IMS Connect is being used, which would translate between the suitable ASCII and EBCDIC character sets.

10.4 Upgrading or Migrating the Oracle Server from Previous Gateways

Follow these instructions only if you have a previous version of the Oracle Procedural Gateway for APPC installed on your system and need to configure it for release 10.2.0.1.0 of the gateway.

1. Upgrade your Oracle Procedural Gateway for APPC to current version levels as follows:

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user SYS.

   2. Install the UTL_RAW package body. From SQL*Plus, run the prvtrawb.plb script from the %ORACLE_HOME%\rdbms\admin directory. This script upgrades the UTL_RAW package body.

      C:\> cd %ORACLE_HOME%\rdbms\admin
      SQL> @prvtrawb.plb
      
      

   3. Install the UTL_PG package body. From SQL*Plus, run the prvtpgb.plb script from the %ORACLE_HOME%\rdbms\admin directory. This script upgrades the UTL_PG package body.

      C:\> cd %ORACLE_HOME%\rdbms\admin
      SQL> @prvtpgb.plb
      
      

   The prvtrawb.plb and prvtpgb.plb scripts should complete successfully. If they fail because specifications do not exist or were invalidated, then consider reinstalling the package specifications as directed in Section 10.4.1, "If You Must Reinstall Package Specifications".

10.5 Optional Configuration Steps to Permit Multiple Users

The following configuration steps are optional. Perform these steps if you want to allow users other than PGAADMIN to perform PG DD operations using PGAU.

1. Create public synonyms for the PG DD to allow other users to access the tables:

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user SYSTEM.

   2. From SQL*Plus, run the pgddcr8s.sql script in the %ORACLE_HOME%\pg4appc\admin directory. This script creates public synonyms for the PG DD.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgddcr8.sql
      
      

2. Create roles for accessing the PG DD, performing definitions of transactions, and generating TIP specifications. The PGAADMIN user can grant these roles to other users as necessary.

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user PGAADMIN.

   2. From SQL*Plus, run the pgddcr8r.sql script in the %ORACLE_HOME%\pg4appc\admin directory. This script creates two roles, PGDDDEF and PGDDGEN. The PGDDDEF role provides SELECT, INSERT, UPDATE, and DELETE privileges against some of the PG DD tables, and select privileges against others, and allows execution of the PGAU DEFINE, GENERATE, REDEFINE, REPORT, and UNDEFINE statements. The PGDDGEN role provides select privileges against the PG DD tables, and allows execution of the PGAU GENERATE and REPORT statements only.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgddcr8r.sql
      
      

3. Grant access to PGA required packages.

   TIP developers require access to the following PL/SQL packages, which are shipped with the Oracle Integrating Server:

   • DBMS_PIPE in the %ORACLE_HOME%\rdbms\admin directory

   • UTL_RAW in the %ORACLE_HOME%\rdbms\admin directory

   • UTL_PG in the %ORACLE_HOME%\rdbms\admin directory

   Explicit grants to execute these packages must be made to TIP developers.

   These grants can be private, as in the following example:

   C:\> sqlplus SYS\pw@database_specification_string 
   SQL> GRANT EXECUTE ON UTL_RAW TO tip_developer; 
   SQL> GRANT EXECUTE ON UTL_PG TO tip_developer; 
   SQL> GRANT EXECUTE ON DBMS_PIPE TO tip_developer; 
   SQL> CONNECT PGAADMIN\pw@database_specification_string 
   SQL> GRANT EXECUTE ON PGAADMIN.PURGE_TRACE TO tip_developer; 
   SQL> GRANT EXECUTE ON PGAADMIN.READ_TRACE TO tip_developer; 
   SQL> GRANT EXECUTE ON PGAADMIN.GPGLOCAL TO tip_developer; 
   SQL> exit
   
   

   Alternatively, these grants can be public, as in the following example:

   C:\> sqlplus SYS\pw@database_specification_string 
   SQL> GRANT EXECUTE ON UTL_RAW TO PUBLIC;
   SQL> GRANT EXECUTE ON UTL_PG TO PUBLIC;
   SQL> GRANT EXECUTE ON DBMS_PIPE to PUBLIC;
   SQL> CONNECT PGAADMIN\pw@database_specification_string 
   SQL> GRANT EXECUTE ON PGAADMIN.PURGE_TRACE TO PUBLIC;
   SQL> GRANT EXECUTE ON PGAADMIN.READ_TRACE TO PUBLIC;
   SQL> GRANT EXECUTE ON PGAADMIN.GPGLOCAL TO PUBLIC;
   SQL> EXIT
   
   

   You can use either private or public grants. Both are sufficient for using PGA. Public grants are easier and can be performed now. If you use private grants, then they must be issued each time a new TIP developer user ID is created.

   SQL scripts for performing these grants are provided in the %ORACLE_HOME%\pg4appc\admin directory. The pgddapub.sql script performs these grants for public access to the packages. The pgddadev.sql script performs the grants for private access to the packages by a single TIP developer. If you are going to use private grants, then you must run the pgddadev.sql script once for each TIP developer's user ID:

   1. Use SQL*Plus to connect to the Oracle Integrating Server as user PGAADMIN.

   2. From SQL*Plus, run the suitable script (pgddapub.sql or pgddadev.sql) from the %ORACLE_HOME%\pg4appc\admin directory. The script performs the necessary grants as described earlier. You are prompted for the required user IDs, passwords, and database specification strings. If you are using private grants, then repeat this step for each user ID requiring access to the packages.

      C:\> cd %ORACLE_HOME%\pg4appc\admin
      SQL> @pgddapub.sql
      
      

      or

      SQL> @pgddadev.sql
      
      

4. If you are upgrading from a previous release of the gateway when the communication protocol was SNA, to the current gateway using TCP/IP, and if you want to upgrade your existing TIPs with new function and maintenance, then regenerate existing TIP specifications using the PGAU GENERATE statement.

   Note:

   The Procedural Gateway Administrative Utility (PGAU) has been enhanced to automatically upgrade existing PG DD entries with a new attribute when a PGAU GENERATE command is executed. To support this enhancement, add a new privilege to the PGDDGEN role. To do this, as the PGAADMIN user, use SQL*Plus to connect to the Oracle Integrating Server where the PG DD is stored. Then, issue the following SQL command:

   SQL> GRANT INSERT ON PGA_DATA_VALUES TO PGDDGEN
   

   1. Call PGAU in the directory path where the PGAU control files are generated and where TIPs are stored:

      C:\> pgau
      PGAU> CONNECT PGAADMIN\pgaadmin@database_specification_string 
      PGAU> GENERATE tranname 
      PGAU> EXIT
      
      

   For more information about the GENERATE command, refer to the PGAU GENERATE command section in Chapter 2 of the Oracle Procedural Gateway for APPC User's Guide.

   Note that it is not necessary to define the PG DD entries again.

5. Call SQL*Plus in the same directory path where the newly-generated TIP specifications are stored.

   C:\> sqlplus tip_owner\pw@database_specification_string 
   SQL> @tipname.pkh 
   SQL> @tipname.pkb
   SQL> exit
   
   

   PGAU GENERATE produces the TIP in two output files, a specification and a body. You must compile both, first the specification and then the body.

   For more information about the GENERATE command, refer to the PGAU GENERATE command section in Chapter 2 of the Oracle Procedural Gateway for APPC User's Guide.

10.6 Configuring TCP/IP for the Gateway

You must now configure the TCP/IP for IMS Connect communication package profiles for TCP/IP connections.

Configure the profiles to define the TCP/IP conversations with the OLTP. Refer to Chapter 7, "Configuring the TCP/IP Communications Package for IMS Connect" for the suitable instructions.

When you have finished configuring your communications package, return to the following section, Section 10.7, "Configuring the Gateway".

10.7 Configuring the Gateway

To configure the gateway, follow the instructions given subsequently:

1. Tailor the gateway parameters.

   There are a number of parameters specific to the Oracle Procedural Gateway for APPC when it is using TCP/IP for IMS Connect. These are supplied in the gateway parameter file, initsid.ora, which is in the %ORACLE_HOME%\pg4appc\admin directory. A sample gateway parameter file, initPGA.ora, is provided in this subdirectory.

   Note:

   In the initsid.ora file, substitute your gateway SID name for "sid " in this file name.

   The initsid.ora file contains both APPC and TCP/IP parameters, separated by a description. You must modify the initsid.ora file by deleting the APPC parameters. Refer to Appendix B, "Gateway Initialization Parameters for TCP/IP Communication Protocol" for the valid TCP/IP parameters.

   The parameters fall into two categories:

   • gateway initialization parameters

     These parameters control the general operation of the gateway in the Oracle environment.

     Important:

     Before performing the following step, refer to Appendix B, "Gateway Initialization Parameters for TCP/IP Communication Protocol" for information about tailoring gateway initialization and PGA parameters. Pay special attention to the information about using the PGA_CAPABILITY parameter.

   • PGA parameters

     PGA parameters control the TCP/IP interface portion of the gateway. Use the SET gateway initialization parameter to specify PGA parameters. Oracle recommends that you group all SET commands for PGA parameters at the end of the initsid.ora file.

     Note:

     Misspelled parameters are ignored. However, if the %ORACLE_HOME%\pg4appc\admin\initsid.ora file is missing, then all calls to the gateway fail and return a PGA-20928 error.

10.8 Loading the PGA_TCP_IMSC Table

Gateway users who wish to employ the TCP/IP protocol do so by using the pg4tcpmap tool.

The pg4tcpmap tool resides on the gateway. Its function is to map the side profile name to TCP/IP and IMS Connect attributes. You must run this tool before executing the PL/SQL gateway statements (such as %ORACLE_HOME%\pg4appc\demo\IMS\pgaims.sql).

In PGAINIT TIP, for example, the user must specify a side profile name. The SNA protocol recognizes and uses the parameter. In this release of the gateway, the pg4tcpmap tool uses the original PGAINIT TIP format to map the relevant SNA parameters to TCP/IP. The pg4tcpmap tool inserts the values of these parameters into a table called PGA_TCP_IMSC.

Before executing pg4tcpmap, you must specify the ORACLE_HOME, Oracle SID and modify initsid.ora. Refer to Appendix B, "Gateway Initialization Parameters for TCP/IP Communication Protocol" in this guide and Chapter 6 in the Oracle Procedural Gateway for APPC User's Guide for complete information about the pg4tcpmap commands.

Chapter 6 of the Oracle Procedural Gateway for APPC User's Guide for Microsoft Windows contains a list of pg4tcpmap commands and instructions for using them, as well as an example of the table. Refer to "Problem Determination" in the Oracle Procedural Gateway for APPC User's Guide for information about the trace file for the executed pg4tcpmap tool.

To operate this tool, execute the following command:

C:\> cd %ORACLE_HOME%\bin
C:\> pg4tcpmap

Refer to "Output for the pg4tcpmap Tool" for a sample of the pg4tcpmap output.

10.9 Verifying the Gateway Installation and OLTP Configuration

To verify the gateway installation and the OLTP configuration, perform the following procedures after installing the gateway.

==> Congratulations, your gateway is communicating with IMS/TM <==

10.10 Performing Postinstallation Procedures

The following are optional steps that you can perform as necessary. Installation of the sample applications for the OLTP is recommended to help you to fully understand how the gateway works and how it interfaces with the OLTP.