Historical Overview  Benefits of DB2 for z/OS  Terminology of DB2 for z/OS  Terminology Mainframe  Example of a JCL job  Comparison System Structures DB2 for z/OS vs. DB2 for Windows, Linux,..  Comparison Commands DB2 for z/OS vs. DB2 for Windows, Linux,..

IBM zSeries Z990

Historical Overview

In 1983, IBM was the first company who released a relational database management system! In the following years the database management system has been approved and in 1995 the "Data sharing" feature has been introduced (see below for its definition). IBM's DB2 Universal Database for OS/390 and z/OS is a relational database management system and has been released on its mainframe operating system OS/390 in 1997. From now it was possible use the Query language over multiple "DB2 Member", due to the invention of "Parallel Sysplex" and "Data Sharing". Furthermore you could make use of tablespaces of a size up to 1 terabyte!!
In IBM's latetest version 8.0 you are allowed to create tables up to 128 Terabytes. Addionaly, IBM zSeries supports the 64-Bit hardware!

Benefits of DB2 for z/OS

IBM's DB2 Universal Database is at the core of mission-critical applications, where companies can't afford downtime. DB2 for z/os with its high scalability, robustness and high availability make this database management system is right platform for companies with a huge amount of data!

Terminology of DB2 for z/OS

• DB2 Subsystem: also called an instance; several subsystems can be installed in the same machine logical partion (LPAR),
• DB2 Data Sharing: the concept of parallel working databases - here "DB2 subsystems" called - using the same underlying data
• DB2 Data (Sharing) Member: Each DB2 subsystem which is part of the "DB2 Data Sharing" concept is called a "DB2 Data Member". They are sharing data and catalog tables of DB2.
• DB2 Data Sharing Group: The composite of all "DB2 Data Sharing Members" is called "DB2 Sharing Group"

Terminology Mainframe

Mainframe Term	UNIX/Linux/Windows Term
Dataset	File
DASD (Direct Access Storage Devices) Volume	Hard disk
Central storage, main storage, main memory, real storage	Main memory, RAM
Expanded storage	Extended storage
CPU, CP	CPU
CPC (Central Processor Complex)	Several CPUs (e.g., SMP system with multiprocessors)
LPAR (Logical Partition)	Partition (e.g., partitioning a hard disk in a PC)
Datasets using SYS1 as the highest level qualifier	Configuration files (e.g., .ini files, .profile file)

Example of a JCL job

Comparison System Structures DB2 for z/OS vs. DB2 for Windows, Linux,..

DB2 S/390 Concept	DB2 Unix,Linux,Windows, OS/2 Analogy
Catalog database (DSNDB06)	SYSCATSPACE tablespace
Directory database (DSNDB01)	N/A
Communications database (CDB), part of the catalog	Database directory, node Directory, DCS directory
Active and archive logs concept	Similar concept as in DB2 S/390
Dual logging supported	Dual logging supported
Bootstrap dataset (BSDS)	SQLOGCTL.LFH
Predefined buffer pools are "created" with -ALTER BUFFERPOOL	Buffer pools are created with CREATE BUFFERPOOL
Hiperpools	Extended Storage (ESTORE)
Resource Limit Facility (DSNRLST)	- The DB2 Governor (db2gov) - Query Patroller
Work file database (DSNDB07)	TEMPSPACE1 tablespace (system temporary tablespace)
TEMP database, for global temporary tables	User temporary tablespace, for global temporary tables
Default database (DSNDB04)	USERSPACE1 tablespace
Can execute queries involving tables of different databases	Cannot execute queries involving tables of different databases (without federation)
Client connects to a DB2 subsystem, not to a particular database	Client connects to a database
DSNZPARM (SET SYSPARM command allows DSNZPARM module to be loaded in memory while DB2 is up, but for some parameters, a -stop db2, -start db2 is still required)	DBM CFG (db2stop, db2start required for new values to be in effect) and DB CFG (all connection need to be terminated for the new values to be in effect on next

Comparison Commands DB2 for z/OS vs. DB2 for Windows, Linux,..

DB2 S/390 Command	DB2 Unix,Linux,Windows, OS/2 Analogy
-STOP DB2	db2stop
-STOP DB2 MODE(FORCE)	db2stop force
-START DB2	db2start
-TERM UTILITY(utility id)	db2 force application
-CANCEL THREAD (token id)	db2 force application
-DISPLAY DATABASE (LOCKS)	db2 get snapshot for locks on
To check the tablespaces that are in restricted status: -DISPLAY DATABASE (*) SPACENAM (*) RESTRICT	To check the status of tablespaces: db2 list tablespaces show detail
-DISPLAY THREAD (*) TYPE(*)	db2 list applications show detail
-DISPLAY UTILITY (*)	db2 list applications show detail
SELECT NAME, TBNAME, COLTYPE, LENGTH, NULLS, DEFAULT FROM SYSIBM.SYSCOLUMNS WHERE TBNAME='' AND TBCREATOR = '';	db2 describe table
SELECT * FROM SYSIBM.SYSTABLES WHERE CREATOR = '';	db2 list tables for schema