node-ibm_db

An asynchronous/synchronous interface for node.js to IBM DB2 and IBM Informix. Async APIs return promises if callback function is not used. Async APIs supports async-await programming style.

• Supported Platforms - Windows64, MacOS64, Linuxx64, Linuxia32, AIX, Linux on IBM Z, Linux on Power PC and z/OS.

• MacOS with M1 Chip - Install x64 version of node.js. ibm_db with arm64 version of node.js is not supported.

• Steps to install ibm_db on MacOS M1/M2 Chip system (arm64 architecture) - Check here.

• SQL1598N Error - It is expected in absence of valid db2connect license. Please click here and read instructions.

• GSKit Error - Check instructions as documented here.

API Documentation

• For complete list of ibm_db APIs and example, please check APIDocumentation.md

• For Secure Database connection using SSL/TSL: Check here.

• Got an issue? Need Help? : Check common issues and suggestion here.

Prerequisite

• Make sure your system has C++ compiler installed that support C++11 standard.

• For non-windows platforms: gcc compiler version >= 8.4, python3, nodejs and make is required to install ibm_db. Default compiler on RHEL 6 does not have the required support. Install a newer compiler or upgrade older one.

• Other required system libraries for Linux OS are: libcrypt, libpam, libxml2, libstdc++, libc, libgcc, libaudit, libeconf, libz, liblzma and libcap-ng. These libraries should come by default with OS. If it is not present in your system, please install it.

• UBI9 has deprecated libcrypt. You need to install libcrypt and libxcrypt-compat on UBI9 manually.

• For Windows: compiler is optional as ibm_db comes with pre-compiled binary on Windows64 for node.js version >= 14.x. To compile code on Windows, VC++ 2015.3 v14.00 (v140) or Visual Studio version >= 2017 is required.

• Python version >= 3.8.0 is required by node-gyp. For z/OS, Python 2.7.13 or higher, but lower than Python 3.0, is required.

• For Docker Linux Container: make sure you have installed make, gcc, g++(gcc-c++), python3.9 and node before installing ibm_db. For root user, use npm install --unsafe-perm ibm_db to install ibm_db.

• While installing ibm_db under a container, if you get libcrypt error, add a line in your scrip to install libcrypt and libxcrypt-compat as this library is not present in most of the container OS. f.e. add a line like below in docker script: RUN apt-get update && apt-get install gcc g++ libcrypt libxcrypt-compat python3 make -y

• For Windows Subsystem for Linux (WSL): Install build-essentials package before installing ibm_db.

• For MacOS: Install XCode from appstore before installing ibm_db. Also, gcc@8 and make is required.

• On distributed platforms, you do need not to install any Db2 ODBC client driver for connectivity. ibm_db itself downloads and installs an odbc/cli driver from IBM website during installation. Just install ibm_db and it is ready for use.

• On z/OS, ODBC driver support is part of IBM Db2 for z/OS 11.0 and 12.0. Please ensure IBM Db2 for z/OS 11.0 or 12.0 is installed on your given LPAR. Ensure you follow the instructions to configure your ODBC driver here.

• On z/OS and other non-Windows platform, GNU make is required to install ibm_db. Execute make -v command before installing ibm_db to make sure you have correct make set in PATH.

• On z/OS only certain versions of node-gyp are supported. This was tested with: z/OS v2.4 Db2 v12.0 node-gyp 3.4.0 npm 3.10.10 ibm_db: 2.8.1

• Recommended version of node.js is >= V16.X. For node.js version < 14.X and ibm_db version > 2.4.1, Visual Studio is required to install ibm_db on Windows.

• For Node.js >= V15.x on RHEL and RHEL 8.x, GCC v8.2.1 is required.

• The latest node.js version using which ibm_db is tested: 23.2.0

Install

You may install the package using npm install command:

npm install ibm_db

You may install ibm_db in quiet mode using either of below commands:

npm install --quiet ibm_db
npm install -q ibm_db

You may install ibm_db in silent mode using either of below commands:

npm install --silent ibm_db
npm install -s ibm_db

When using ibm_db in a package.json file, you can set below environment variables to install ibm_db in --quiet or --silent mode:

export npm_config_loglevel=warn   => For quiet mode installation.
export npm_config_loglevel=silent => For silent mode installation.

For ELECTRON or VSCode Installation:

npm install ibm_db -electron=<electron_version>
npm install ibm_db -electron="25.9.2"
npm install ibm_db -vscode

To install using specific version of clidriver from https://public.dhe.ibm.com/ibmdl/export/pub/software/data/db2/drivers/odbc_cli/:

npm install ibm_db -clidriver=<version>
npm install ibm_db -clidriver=v11.1.4
npm install ibm_db -clidriver=v11.5.6

For Docker Linux Container, use below commands:

yum install make gcc gcc-c++ kernel-devel openssl-devel bzip2-devel
install python3.x
install node.js
npm install --unsafe-perm ibm_db

Alpine Linux is not supported by ibm_db as it is an arm64 architecture.

• npm install ibm_db internally downloads and install platform specific clidriver of recent release from here. To avoid this download, you can manually download clidriver from this location or install any verison of IBM Data Server Driver Package or Db2 Client or Sever in your system and point the install directory using IBM_DB_HOME environment variable. If IBM_DB_HOME or IBM_DB_INSTALLER_URL is set, npm install ibm_db do not download clidriver.

• ibm_db works with all supported versions of Db2 Client and Server. Instead of using open source driver specific clidriver for ibm_db, you may download and install DSDRIVER or DB2Client from IBM Fix Central or IBM Passport Advantage of Db2 V11.1.0.0 onwards.

• If IBM_DB_HOME or IBM_DB_INSTALLER_URL is not set, ibm_db always downloads open source driver specific clidriver and use it. Ignores any other installation.

For more installation details please refer: INSTALLATION GUIDE

If installation fails while downloading clidriver, follow instructions as documented here.

Validate your installation

• Update database connection info in node_modules\ibm_db\test\config.json file.
• Run node node_modules\ibm_db\test\test-basic-test.js command.

Important Environment Variables and Download Essentials

IBM_DB_HOME :

• USE:

  • On distributed platforms, set this environment variable if you want to avoid downloading of clidriver from the IBM Hosted URL or from the internet.
  • On z/OS, set this environment variable to the High Level Qualifier (HLQ) of your Db2 datasets. During npm install, the module will automatically reference ODBC driver header files under: $IBM_DB_HOME.SDSNC.H and the sidedeck definitions in $IBM_DB_HOME.SDSNMACS(DSNAO64C) to build the node binding.

• HOW:

  • On distributed platforms, set IBM_DB_HOME environment variable to a pre-installed db2 client or server installation directory.
  • On z/OS, set IBM_DB_HOME environment variable to the High Level Qualifier (HLQ) of your Db2 datasets. For example, if your Db2 datasets are located as DSNC10.SDSNC.H and DSNC10.SDSNMACS, you need to set IBM_DB_HOME environment variable to DSNC10 with the following statement (can be saved in ~/.profile):

IBM_DB_INSTALLER_URL :

• USE:

  • Set this environment variable to by-pass the IBM Hosted URL for downloading odbc/clidriver.

• HOW:

  • Set IBM_DB_INSTALLER_URL environment variable with alternate odbc/clidriver downloading URL link or with locally downloaded "tar/zipped clidriver's parent directory path.

• TIP:

  • If you don't have alternate hosting URL then, you can download the tar/zipped file of clidriver from the IBM Hosted URL and can set the IBM_DB_INSTALLER_URL environment variable to the downloaded "tar/zipped clidriver's" parent directory path. No need to untar/unzip the clidriver and do not change the name of downloaded file.

DOWNLOAD_CLIDRIVER :

• USE:

  • Set this environment variable to force downloading of odbc/clidriver. If clidriver is already present, existing clidriver will get deleted. If IBM_DB_HOME environment variable is set, still clidriver will get downloaded by ignoring value of IBM_DB_HOME.

• HOW:

  • On distributed platforms, Set DOWNLOAD_CLIDRIVER environment variable to true to force downloading of clidriver from IBM hosted URL. Never set DOWNLOAD_CLIDRIVER on z/OS system.

Download clidriver (based on your platform & architecture) from the below IBM Hosted URL:

DOWNLOAD CLI DRIVER

Cli Drivers for Specific Platform and Architecture

|Platform |Architecture |Cli Driver |Supported | | :---: | :---: | :---: | :---: | |AIX | ppc |aix32_odbc_cli.tar.gz | Yes | | | others |aix64_odbc_cli.tar.gz | Yes | |Darwin | x64 |macos64_odbc_cli.tar.gz | Yes | |Linux | x64 |linuxx64_odbc_cli.tar.gz | Yes | | | s390x |s390x64_odbc_cli.tar.gz | Yes | | | s390 |s390_odbc_cli.tar.gz | Yes | | | ppc64 (LE) |ppc64le_odbc_cli.tar.gz | Yes | | | ppc64 |ppc64_odbc_cli.tar.gz | Yes | | | ppc32 |ppc32_odbc_cli.tar.gz | Yes | | | others |linuxia32_odbc_cli.tar.gz| Yes | |Windows | x64 |ntx64_odbc_cli.zip | Yes | | | x32 |nt32_odbc_cli.zip | Not supported with node-ibm_db | |z/OS | s390x |ODBC support from IBM Db2 for z/OS 11.0 or 12.0 | Yes |

• For MacOS M1 Chip system with arm64 architecture, install x64 version of node.js and gcc@8. ibm_db with arm64 version of node.js is not supported. For installation instruction, check here.

Configure ODBC driver on z/OS

Please refer to the ODBC Guide and References cookbook for how to configure your ODBC driver. Specifically, you need to:

1. Apply Db2 on z/OS PTF UI60551 to pick up new ODBC functionality to support Node.js applications.

2. Bind the ODBC packages. A sample JCL is provided in the SDSNSAMP dataset in member DSNTIJCL. Customize the JCL with specifics to your system.

3. Ensure users that should be authorized have authority to execute the DSNACLI plan. Included are samples granting authority to public (all users), or specific groups via SQL GRANT statements, or alternately via RACF. The security administrator can use these samples as a model and customize/translate to your installation security standards as appropriate.

   Examples using SQL GRANT statement:

   Example 1: Grant the privilege to execute plan DSNACLI to RACF group, DBCLIGRP.

    GRANT EXECUTE ON PLAN DSNACLI TO DBCLIGRP;

   Example 2: Grant the privilege to execute plan DSNACLI to all users at the current server.

    GRANT EXECUTE ON PLAN DSNACLI TO PUBLIC;

   Examples using Access Control Authorization Exit for Db2 authorization:

   Define profile for plan DSNACLI execute privilege check

    RDEFINE MDSNPN DB2A.DSNACLI.EXECUTE UACC(NONE) OWNER(DB2OWNER)

   Example 1: PERMIT the privilege to execute plan DSNACLI to RACF group, DBCLIGRP

    PERMIT DB2A.DSNACLI.EXECUTE ID(DBCLIGRP) ACCESS(READ) CLASS(MDSNPN)

   Example 2: PERMIT the privilege to execute plan DSNACLI to all users at the current server

    PERMIT DB2A.DSNACLI.EXECUTE ID(*) ACCESS(READ) CLASS(MDSNPN)

   Issue SETROPTS command to refresh in-storage profile lists

     SETR RACLIST(MDSNPN) REFRESH

4. Update the STEPLIB environment variable to include the Db2 SDSNEXIT, SDSNLOAD and SDSNLOD2 data sets. You can set the STEPLIB environment variable in your .profile with the following statement, after defining IBM_DB_HOME to the high level qualifier of your Db2 datasets as instructed above:

   # Assumes IBM_DB_HOME specifies the HLQ of the Db2 datasets.
   export STEPLIB=$STEPLIB:$IBM_DB_HOME.SDSNEXIT:$IBM_DB_HOME.SDSNLOAD:$IBM_DB_HOME.SDSNLOD2

5. Configure an appropriate Db2 ODBC initialization file that can be read at application time. You can specify the file by using either a DSNAOINI data definition statement or by defining a DSNAOINI z/OS UNIX environment variable. For compatibility with ibm_db, the following properties must be set:

   In COMMON section:

   MULTICONTEXT=2
   CURRENTAPPENSCH=ASCII
   FLOAT=IEEE

   In SUBSYSTEM section:

   MVSATTACHTYPE=RRSAF

   Here is a sample of a complete initialization file:

   ; This is a comment line...
   ; Example COMMON stanza
   [COMMON]
   MVSDEFAULTSSID=VC1A
   CONNECTTYPE=1
   MULTICONTEXT=2
   CURRENTAPPENSCH=ASCII
   FLOAT=IEEE
   ; Example SUBSYSTEM stanza for VC1A subsystem
   [VC1A]
   MVSATTACHTYPE=RRSAF
   PLANNAME=DSNACLI
   ; Example DATA SOURCE stanza for STLEC1 data source
   [STLEC1]
   AUTOCOMMIT=1
   CURSORHOLD=1

6. Please make sure tagging of your odbc.ini file is "binary" or "mixed":

   chtag -b $DSNAOINI
   or
   chtag -m -c IBM-1047 $DSNAOINI

   If file is tagged text (chtag -t -c IBM1047 $DSNAOINI) the S0C4 abend occurs.

   Reference Chapter 3 in the ODBC Guide and References for more instructions.

How to get ibm_db instance?

The simple api is based on the instances of Database class. You may get an instance by one of the following ways:

require("ibm_db").open(connectionString, function (err, conn){
  //conn is already open now if err is falsy
});

or by using the helper function:

var ibmdb = require("ibm_db")();

or by creating an instance with the constructor function:

var Database = require("ibm_db").Database
  , ibmdb = new Database();

Quick Example

var ibmdb = require('ibm_db');
var connStr = "DATABASE=<dbname>;HOSTNAME=<myhost>;UID=db2user;PWD=password;PORT=<dbport>;PROTOCOL=TCPIP";

ibmdb.open(connStr, function (err,conn) {
  if (err) return console.log(err);
  
  conn.query('select 1 from sysibm.sysdummy1', function (err, data) {
    if (err) console.log(err);
    else console.log(data);

    conn.close(function () {
      console.log('done');
    });
  });
});

ibmdb.open(connStr).then(
    conn => {
      conn.query("select 1 from sysibm.sysdummy1").then(data => {
        console.log(data);
        conn.closeSync();
      }, err => {
        console.log(err);
      });
    }, err => {
      console.log(err)
    }
);

main();
async function main() {
  try {
    let conn = await ibmdb.open(cn);
    await conn.query("drop table mytab").catch((e) => {console.log(e);});
    await conn.query("create table mytab(c1 int, c2 varchar(10))");
    await conn.query("insert into mytab values (?, ?)", [3, 'ibm']);
    let stmt = await conn.prepare("select * from mytab");
    let result = await stmt.execute();
    data = await result.fetchAll();
    console.log("result = ", data);
    await result.close();
    await stmt.close();
    await conn.close();
  } catch(e) {
      console.log(e);
  }
}

Un-Install

npm uninstall ibm_db

OR, just delete the node_modules\ibm_db directory manually from your system.

For z/OS and iSeries Connectivity and SQL1598N error

• Connection to Db2 for z/OS or Db2 for i(AS400) Server using ibm_db driver from distributed platforms (Linux, Unix, Windows and MacOS) is not free.

• Connection to Db2 for LUW or Informix Server using ibm_db driver is free.

• ibm_db returns SQL1598N error in absence of a valid db2connect license. SQL1598N error is returned by the Db2 Server to client. To suppress this error, Db2 server must be activated with db2connectactivate utility OR a client side db2connect license file must exist.

• Db2connect license can be applied on database server or client side. A db2connect license of version 11.5 is required for ibm_db.

• Ask your DBA to run db2connectactivate utility on Server to activate db2connect license.

• If database Server is enabled for db2connect, no need to apply client side db2connect license.

• If Db2 Server is not db2connectactivated to accept unlimited number of client connection, you must need to apply client side db2connect license.

• db2connectactivate utility and client side db2connect license both comes together from IBM in a single zip file.

• Client side db2connect license is a db2con*.lic file that must be copied under clidriver\license directory.

• User running application must have write permission for clidriver\cfgcache and clidriver\license directories as clidriver need to create binary files to store licensing info in these directories at runtime. Lack of permission to create file too causes SQL1598N error.

• If you have a db2jcc_license_cisuz.jar file, it will not work for ibm_db. db2jcc_license_cisuz.jar is a db2connect license file for Java Driver. For non-Java Driver, client side db2connect license comes as a file name db2con*.lic.

• If environment variable IBM_DB_HOME or IBM_DB_INSTALLER_URL is not set, ibm_db automatically downloads open source driver specific clidriver from https://public.dhe.ibm.com/ibmdl/export/pub/software/data/db2/drivers/odbc_cli and save as node_modules\ibm_db\installer\clidriver. Ignores any other installation.

• If IBM_DB_HOME or IBM_DB_INSTALLER_URL is set, you need to have same version of db2connect license as installed db2 client. Check db2 client version using db2level command to know version of db2connect license required. The license file should get copied under $IBM_DB_HOME\license directory.

• If you do not have db2connect license, contact IBM Customer Support to buy db2connect license. Find the db2con*.lic file in the db2connect license shared by IBM and copy it under .../node_modules/ibm_db/installer/clidriver/license folder to be effective.

• To know more about license and purchasing cost, please contact IBM Customer Support.

For AIX install issue

If npm install ibm_db aborts with "Out Of Memory" error on AIX, first run ulimit -d unlimited and then npm install ibm_db.

If installation fails while downloading clidriver

• If installation of ibm_db fails because ibm_db fails to download *_odbc_cli.tar.gz or *_odbc_cli.zip file, it is most likely that your firewall or VPN configuration is blocking download of this file from internet. In this case, manually download the platform specific clidriver from DOWNLOAD CLI DRIVER or github repo; untar/unzip it, you'll get clidriver directory.

• Set a system level environment variable IBM_DB_HOME=<full path of clidriver directory> and then run npm install ibm_db.

• Example for non-Windows:

export IBM_DB_HOME=/home/$USER/clidriver
npm install ibm_db

• Example for Windows:

set IBM_DB_HOME=C:\myproject\clidriver
npm install ibm_db

For Missing Package/Binding issue

If your application is able to connect to IBM Database Server but query execution is throwing SQL0805N error, run below commands to fix the package related issues:

cd .../ibm_db/installer
source setenv.sh
db2cli bind $IBM_DB_HOME/bnd/@db2cli.lst -database <dbname>:<hostname>:<port> -user <dbuser> -passwd <passwd> -options "grant public action replace blocking no"

If above command prints 0 error at end, then you can proceed to run query. If it reports non-zero error, open a new issue on github and share the output of above db2cli bind command along with query execution error.

Alternatively, if you have any other DB2 client with CLP, you can bind packages using db2 bind command too. f.e. use below command against DB2 for z/OS server:

db2 bind .../sqllib/bnd/@ddcsmvs.lst action replace grant public sqlerror continue messages msg.txt

Note: "db2cli bind" command print the logs on output prompt, so you need to redirect output to some file to capture it. To capture logs of "db2 bind" command, you need to use messages option as in above example. Note: "db2cli bind" does not work with DB2 z/OS if the CLI packages (SYSSH*) were bound the DB2 subsystem is configured with APPLCOMPAT and SQLLEVEL set to V12R1M502 or higher. Tested with APPLCOMPAT=V12R1M500

Troubleshooting on z/OS

Some errors on z/OS are incomplete, so, to debug, add the following to your Db2 ODBC initialization file:

 APPLTRACE=1
 APPLTRACEFILENAME=/u/<username>/odbc_trace.txt

Db2 z/OS: UnicodeDecodeError Exception

• Make sure you have set CURRENTAPPENSC=ASCII or UNICODE in ODBC initialization file.
• Make sure tagging of your ODBC ini file is "binary" or "mixed".

Usage within VS Code

If you are using ibm_db to develop extension for VS Code, then ibm_db has to be rebuilt with Electron libraries. This can be achieved by running:

npm install ibm_db -vscode

ibm_db would automatically be rebuilt with Electron if your installation directory path contains 'db2connect' as a sub-string. This has the same effect as running with '-vscode' flag.

How to verify database connectivity using ODBC and generate db2trace?

cd to ibm_db/installer directory and update database connection information for db2cli validate command in testODBCConnection.sh file for non-Windows platform and execute it. For Windows platform, update connection info for db2cli validate command in testODBCConnection.bat file and execute it from Administrator Command Prompt. Script testODBCConnection set the required environment variables, validate database connectivity and gerate db2trace files.

How to get db2trace for any node.js test file?

copy test.js to ibm-db/test directory
cd ibm_db/installer
source ./setenv.sh
cd ibm_db/test
./trace test.js

trace script works only on non-windows platform. For Windows, use testODBCConnection.bat script. You can replace db2cli validate command with node test.jsin testODBCConnection.bat script and execute it.

Issues while connecting to Informix Server

While using ibm_db against Informix server, you may get few issues if server is not configured properly. Also, ibm_db connects to only DRDA port. So, make sure drsoctcp of Informix is configured.

SQL1042C Error

If ibm_db is returning SQL1042C error while connecting to server, use "Authentication=SERVER" in connection string. It should avoid the error. Alternatively, you can set Authentication in db2cli.ini file or db2dsdriver.cfg file too. This error mostly comes due to presence of multiple copy of db2 client or gskit library in the system. Run db2level command and it shows path other than ibm_db\installer\clidriver, set IBM_DB_HOME to this path and reinstall ibm_db. If you have C:\Program Files\IBM\gsk8 directory on windows, remove it from PATH env var and if possible, rename it.

code-set conversion error

If Informix server is not enabled for UNICODE clients or some code-set object file is missing on server; server returns this error to ibm_db: [IBM][CLI Driver][IDS/UNIX64] Error opening required code-set conversion object file.

To avoid this error, remove UNICODE from binding.gyp file and rebuild the ibm_db.

Also to avoid above issues, you can run ibm_db/installer/ifx.sh script on non-windows system.

Need Help?

If you encountered any issue with ibm_db, first check for existing solution or work-around under issues or on google groups forum. Links are:

https://github.com/ibmdb/node-ibm_db/issues https://groups.google.com/forum/#!forum/node-ibm_db

If no solution found, you can open a new issue on github.

Getting SQL30081N error occasionally, after some time of inactivity : Check issue#810

Want to configure db2dsdrivre.cfg file to avoid SQL30081N error: Check issue#808

Build Options

Debug

If you would like to enable debugging messages to be displayed you can add the flag DEBUG to the defines section of the binding.gyp file and then execute node-gyp rebuild.

<snip>
'defines' : [
  "DEBUG"
],
<snip>

OR,

cd ibm_db
npm install --debug

Above two method will enable debugging messages from C++ code. You can enable debugging messages from nodejs code by calling ibmdb.debug(true) api from your application.

Unicode

By default on distributed platforms, UNICODE suppport is enabled. This should provide the most accurate way to get Unicode strings submitted to your database. For best results, you may want to put your Unicode string into bound parameters.

On z/OS, UNICODE is disabled by default.

However, if you experience issues or you think that submitting UTF8 strings will work better or faster, you can remove the UNICODE define in binding.gyp

<snip>
'defines' : [
  "UNICODE"
],
<snip>

timegm vs timelocal

When converting a database time to a C time one may use timegm or timelocal. See man timegm for the details of these two functions. By default the node-ibm_db bindings use timelocal. If you would prefer for it to use timegm then specify the TIMEGM define in binding.gyp

<snip>
'defines' : [
  "TIMEGM"
],
<snip>

Strict Column Naming

When column names are retrieved from DB2 CLI, you can request by SQL_DESC_NAME or SQL_DESC_LABEL. SQL_DESC_NAME is the exact column name or none if there is none defined. SQL_DESC_LABEL is the heading or column name or calculation. SQL_DESC_LABEL is used by default and seems to work well in most cases.

If you want to use the exact column name via SQL_DESC_NAME, enable the STRICT_COLUMN_NAMES define in binding.gyp

<snip>
'defines' : [
  "STRICT_COLUMN_NAMES"
],
<snip>

Tips

Using more than 4 threads on Linux

Be aware that through node v0.9 the uv_queue_work function, which is used to execute the ODBC functions on a separate thread, uses libeio for its thread pool. This thread pool by default is limited to 4 threads.

This means that if you have long running queries spread across multiple instances of ibmdb.Database() or using odbc.Pool(), you will only be able to have 4 concurrent queries.

You can increase the thread pool size by using @developmentseed's [node-eio] (https://github.com/developmentseed/node-eio).

install:

npm install eio

usage:

var eio = require('eio'); 
eio.setMinParallel(threadCount);

Contributor

• Dan VerWeire ([email protected])
• Lee Smith ([email protected])
• Bruno Bigras
• Christian Ensel
• Yorick
• Joachim Kainz
• Oleg Efimov
• paulhendrix
• IBM

Contributing to the node-ibm_db

Contribution Guidelines

Contributor should add a reference to the DCO sign-off as comment in the pull request(example below):
DCO Signed-off-by: Random J Developer <[email protected]>

License

Copyright (c) 2013 Dan VerWeire [email protected]

Copyright (c) 2010 Lee Smith [email protected]

Copyright (c) 2014 IBM Corporation

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.