Quick Start in accessing Db2 for z/OS from a GO application.

GO/GoLang is an open source programming language that is getting popular in the recent years because of its performance, memory usage, built-in concurrency mechanism, and powerful libraries, etc.

In this blog, I am going to show you how to to connect to Db2 for z/OS using a GO application and perform some basic database operations.

Here is my setup:

• Ubuntu 18
• Db2 11 for z/OS

Pre-requisites

Activation utility is ran in the Db2 server. Otherwise, ODBC license file for Db2 for z/OS is required

Step 1 : Install GO

I install GO in /root directory, you can install in any directory you want.

wget https://dl.google.com/go/go1.11.2.linux-amd64.tar.gz
tar -C /usr/local -xzf go1.11.2.linux-amd64.tar.gz

Details can be found in GO website.

Add following to /root/.bashrc so the GO environment is setup whenever you login.

export PATH=$PATH:/usr/local/go/bin
export GOPATH=/root/go/

Step 2 : Install go_ibm_db

Install go_ibm_db from GitHub

go get -d github.com/ibmdb/go_ibm_db

ibmdb will be installed in /root/go/src/github.com

Step 3 : Install CLIdriver

You can skip this step if you already installed CLIdriver.

cd /root/go/src/github.com/ibmdb/go_ibm_db/installer
chmod 777 setup.go
go run ./setup.go

Step 4 : Install gcc

You can skip this step if you already have gcc installed.

sudo apt update
apt install gcc 
gcc --version

Step 5: Implement your first database GO application

Below is an application (example1.go) I adapted from GitHub to select first 3 rows from a catalog table. I have to admit there is plenty of room for improvement (like error handling, etc.).

To make the application easy to read, I put everything in main() . If you have implemented database application before, you will see familiar steps here:

• import required libraries
• connect to your database
• specify a query. In this application, I select first 3 rows from a catalog table.
• prepare the query
• execute the query
• loop through the resultset, print out the resultset.
• close the connection

package main
import (
    _ "github.com/ibmdb/go_ibm_db"
   "database/sql"
   "fmt"
)
func main(){
con:="HOSTNAME=<host>;DATABASE=<name>;PORT=<number>;UID=<username>;PWD=<password>"
    
db, err:=sql.Open("go_ibm_db", con)
    if err != nil{
       fmt.Println(err)
    }
query := "SELECT STRINGID, SUBSTR(STRING,1,60) AS STRING FROM SYSIBM.SYSXMLSTRINGS ORDER BY STRINGID FETCH FIRST 3 ROWS ONLY"
    
st, err:=db.Prepare(query)
    if err !=nil{
       fmt.Println(err)
    }
rows, err:=st.Query()
    if err!=nil{
       fmt.Println(err)
    }
cols,  _:=rows.Columns()
    fmt.Printf("%s    %s\n",cols[0],cols[1])
    fmt.Println("-------------------------------------")
defer rows.Close()
    for rows.Next(){
       var strid,str string
       err = rows.Scan(&strid, &str)
       if err !=nil{
         fmt.Println(err)
       }
       fmt.Printf("%v        %v\n",strid,str)
    }
    db.Close()
}

Note: remember to update this line with your own Db2 info

con:="HOSTNAME=<host>;DATABASE=<name>;PORT=<number>;UID=<username>;PWD=<password>"

Step 6 : Execute your GO application

Setup your environment variables.

export DB2HOME=/root/go/src/github.com/ibmdb/go_ibm_db/installer/clidriver
export CGO_CFLAGS=-I$DB2HOME/include
export CGO_LDFLAGS=-L$DB2HOME/lib
export LD_LIBRARY_PATH=$DB2HOME/lib

Run your application

go run example1.go

Sample output:

STRINGID    STRING
-------------------------------------
1001        product
1002        description
1003        name

Troubeshooting

1. License issue

SQLDriverConnect: {42968} [IBM][CLI Driver] SQL1598N An attempt to connect to the database server failed because of a licensing problem. SQLSTATE=42968

This can be solved by executing the activation utility or copying the Db2 for z/OS license file db2consv_zs.lic to /root/go/src/github.com/ibmdb/go_ibm_db/installer/clidriver/license directory.

2. -805 error

SQLExecute: {51002} [IBM][CLI Driver][DB2] SQL0805N  Package "STLEC1.NULLID.SYSSH200.5359534C564C3031" was not found.  SQLSTATE=51002

Contact your System Admin to bind the ODBC packages.