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Legacy technologies in corporate environments. My background. Experience since 1970 in InformationTechnology. Companies where I’ve worked : Private and State companies; Banks; IT Services Providers; Areas and activities in which I’ve been involved : IT Planning;

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Legacy technologies in corporate environments

Legacy technologies in corporate environments – Alberto R. Schiesari – jan/2008


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My background

Experience since 1970 in InformationTechnology.Companies where I’ve worked :

Private and State companies;

Banks;

IT Services Providers;

Areas and activities in which I’ve been involved :

IT Planning;

Software Factory;

Training;

Appl Systems Dev & Maint (systems analysis and programming);

Technical Support (system programmer). And, since 1981

I’m also an University Teacher (Computing Sciences courses)

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Abstract

ABSTRACT

Even today, most large corporations (in both developing and developed countries) still rely on 'legacy' technologies such as mainframes for daily operations. In this talk, I will present a review of the characteristics of the mainframes and related technology, the suppliers, the legacy systems user’s profile, and the roles that these technologies play, including software development and maintenance. Finally, I’ll present some trends we can observe in the corporations in the use of legacy systems.

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Outline

  • 1. Mainframe concept

    • 1.1 In the sixties

    • 1.2 Suppliers

    • 1.3 Characteristics

  • 2. Mainframe users

  • 3. Mainframe legacy systems

    • 3.1 Some words about software assets

    • 3.2 Hardware and Software survival

    • 3.3 Application Software survival

    • 3.4 People

    • 3.5 Trends

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1. Mainframe Concept

  • 1. Mainframe concept

    • 1.1 In the sixties

    • 1.2 Suppliers

    • 1.3 Characteristics

  • 2. Mainframe users

  • 3. Mainframe legacy systems

    • 3.1 Some words about software assets

    • 3.2 Hardware and Software survival

    • 3.3 Application Software survival

    • 3.4 People

    • 3.5 Trends

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Was once the 60’s…

1. Mainframe Concept

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1. Mainframe Concept

  • 1.1 In the 60’s

  • There were no small systems

  • 3rd generation computers:

    • Integrated Circuits

    • Operating systems

    • Multiprogramming

    • Centralized processing

We could see a bit with the naked eye

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1. Mainframe Concept

1.2 Mainframe suppliers

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1. Mainframe Concept

1.2 Mainframe suppliers

Who’s left today? Basically IBM.

So, when we talk about Mainframes today, we’re talking about IBM systems, derived from IBM/360.

/360 model 30 : (ex.) 64 K Ram, no virtual storage, 3 programs, 1 card reader/punch, 4 X 7.5 MB 2311 HD, 1403 printer (1100 lpm),

2420 magnetic tapes, typewriter console

http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2030.html

The concept is not necessarily attached to processing capacity or speed, but to the systems (and the product of their evolution) developed based on the technical characteristics of the original IBM mainframes.

Hardware, base software (operating systems) and application systems.

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1. Mainframe Concept

1.2 Mainframe suppliers :

mainframes X servers X supercomputers

IBM products today are servers that also do (the “old”) mainframe activities.

CPU = eServer zSeries 990, max 256 GB RAM, 2007 kg, 1,94 m height, 26.78 sq. ft footprint, 58.69 sq.ft clearance, 15.8 kw, 53.73 KBTU/hr

http://www-03.ibm.com/systems/z/hardware/z990/glance.html

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1. Mainframe Concept

1.2 Mainframe suppliers :

mainframes X servers X supercomputers

Systems not derived from the IBM System/360 (even with similar processing power) are referred to as "servers“ or, in other cases, …

HP Superdome Server , up to 64 processors, up to 2 TB memory, 77” height, 60” width, 48” depth

http://www.hp.com/products1/servers/scalableservers/superdome/comparison.html

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1. Mainframe Concept

1.2 Mainframe suppliers :

mainframes X servers X supercomputers

… or, in other cases, supercomputers.

CPU = Cray XT3 , 102200 GFlops ≈ 1/10 teraFlops

http://www.jlab.org/news/releases/2007/supercomputer.html

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1. Mainframe Concept

1.2 Mainframe suppliers :

mainframes X servers X supercomputers

By the way…

IBM Blue Gene /L Supercomputer

73728 GB main memory, 478,200 GFlops = almost half aTeraFlop

# 1 in Top 10 [supercomputer] systems

http://www.top500.org

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1. Mainframe Concept

1.3 Some mainframe characteristics

Application systems programming

In the beginning was cards...

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1. Mainframe Concept

  • 1.3 Some mainframe characteristics

  • Systems designed initially with:

  • Batch processing

  • Primary input data using punched cards

  • (note that even the operating systems were batch-oriented)

http://www.kloth.net/services/cardpunch.php

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1. Mainframe Concept

1.3 Some mainframe characteristics

Evolution: Need for online processing

3270 terminal characteristics

□ (No mouse… only keyboard…no processing capability…)

□ 24 lines X 80 columns = 1920 characters screen

□ Each character is 8 x 20 dot-matrix

□ Each field has his own attributes (color…, blinking, etc)

□ Today : the mainframe applications normally think they’re

communicating with a 3270 or similar, but there is an emulation

program in the PCs, converting protocols

□ Some differences with PC keyboards

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1. Mainframe Concept

1.3 Some mainframe characteristics

3270 keyboard

PC keyboard

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1. Mainframe Concept

1.3 Some mainframe characteristics

Typical 3270 screen

14:04:11 ***** NATURAL TEST UTILITIES ***** 14/06/2007

Test Mode OFF - Debug Main Menu - Object RHALBE18

Code Function

T Set test mode ON

E Debug environment maintenance

S Spy maintenance

B Breakpoint maintenance

W Watchpoint maintenance

C Call statistics maintenance

X Statement execution statistics maintenance

V Variable maintenance

L List object source

? Help

. Exit

Code .. _ Object name .. ________

Command ===>

Enter-PF1---PF2---PF3---PF4---PF5---PF6---PF7---PF8---PF9---PF10--PF11--PF12---

Help Exit Last Flip Canc

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1. Mainframe Concept

1.3 Some mainframe characteristics

  • Main Operating Systems “lines”

    • (MVT),…,OS/VS2, ..., MVS, ..., z/OS

    • (DOS),…,DOS/VSE,…...…….., z/VSE

  • ….….,VM, .........................., z/VM

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1. Mainframe Concept

1.3 Some mainframe characteristics

□ JCL (“script” language)

□ Vsam (access method)

□ Utilities, compilers

□ etc…

Are functionally quite similar to their previous versions

(the internals were probably completely re-written)

Sintax : max. 80 positions (remember? Punched card...)

//EPC##ARS JOB ('VERIFY'),'VERIFY',CLASS=1,MSGCLASS=X Job to be done

//*-------------------------------------------------- comment

//STEP1 EXEC PGM=IDCAMS Name of program to be executed

//EMPLOYS DD DSN=DSVAABPS.FIN.A999,DISP=(OLD,KEEP) File # 1 program will use

//SYSIN DD * File # 2 program will use (instream data)

VERIFY FILE(EMPLOYS) this is the file #2 contents

//SYSPRINT DD SYSOUT=* File # 3 program will use

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1. Mainframe Concept

  • 1.3 Some mainframe characteristics

  • Compatibility with previous environments provided, to preserve investments (and therefore, clients): applications developed decades ago can be run, in some cases even without recompiling, in the ultimate versions of hardware and software

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1. Mainframe Concept

1.3 Some mainframe characteristics

  • Internal machine code EBCDIC (not ASCII)

    □ Data conversion needed in communication with PCs

  • Text-oriented (normally no graphical processing; no graphical objects)

PC (Ascii code)

Out = “I LOVE YOU”

Hex’49204C4F564520594F55’

In =“ME TOO”

Hex’4D4520544F4F’

Mainframe (Ebcdic code)

In = “I LOVE YOU”

Hex’C940D3D6E540E8D6E4’

Out = “ME TOO”

Hex’D4C540E3D6D6’

I LOVE YOU

ME TOO

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1. Mainframe Concept

  • 1.3 Some mainframe characteristics

  • Evolution : online processing

  • For the application systems:

  • IBM solution : a “driver” to manage online applications

  • CICS = was (and still is...) responsible for managing the resources demanded by most online applications (storage, files, CPU use, locks,...)

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Operating System

Terminals and other remote objetcts

Batch Job

Batch Job

CICS

Nucleus

services

DB2 Dbms

services

services

services

Transactions (programs)

Online (realtime) applications

All in the Cics address space(s)

Batch applications

1 address space each

DB2

Vsam files

1. Mainframe Concept

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1. Mainframe Concept

1.3 Some mainframe characteristics

CICS is not a programming language; user has a set of commands to demand services to CICS, and a host language is needed (ok, we can use it in another way, without a host language, but just for development / test purposes…).

It can be Cobol, PL/I, C, … : CICS commands embedded in the host language commands

About CICS use, see http://websphere.sys-con.com/read/46839.htm

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1. Mainframe Concept

1.3 Some mainframe characteristics

Some alternatives to host language with CICS:

IBM = CSP (discontinued), Visual AGE.

Non-IBM (Software AG) = Natural [+ Adabas] + Cics

(Natural = programming language; can also be used to develop batch applications )

(Adabas = DBMS)

Most mainframe online applications worldwide are created using these tools.

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1. Mainframe Concept

1.3 Some mainframe characteristics

Evolution : online processing

For development support : IBM solution = TSO

Menu Help

------------------------------------------------------------------------------

Utility Selection Panel

1 Library Compress or print data set. Print index listing. Print,

rename, delete, browse, edit or view members

2 Data Set Allocate, rename, delete, catalog, uncatalog, or display

information of an entire data set

3 Move/Copy Move, or copy members or data sets

4 Dslist Print or display (to process) list of data set names.

Print or display VTOC information

5 Reset Reset statistics for members of ISPF library

6 Hardcopy Initiate hardcopy output

7 Transfer Download ISPF Client/Server or Transfer data set

8 Outlist Display, delete, or print held job output

9 Commands Create/change an application command table

11 Format Format definition for formatted data Edit/Browse

12 SuperC Compare data sets (Standard Dialog)

13 SuperCE Compare data sets Extended (Extended Dialog)

14 Search-For Search data sets for strings of data (Standard Dialog)

15 Search-ForE Search data sets for strings of data Extended (Extended Dialog)

Option ===> 

F1=Help F2=Split F3=Exit F7=Backward F8=Forward F9=Swap

F10=Actions F12=Cancel

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1. Mainframe Concept

1.3 Some mainframe characteristics

Program Samples

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1. Mainframe Concept

Cobol CICS

To produce this simple text screen …

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1. Mainframe Concept

Cobol CICS

You have to specify this “physical map” …

(believe it or not : in Assembler language;

OK… there are some cheap or easier alternatives to do the same…)

More...

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1. Mainframe Concept

Cobol CICS

And this “logical map” …

And a program like that… (see next 2 pages)

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Cobol as the host language

In red, the CICS embedded commands

1. Mainframe Concept

Cobol CICS

IDENTIFICATION DIVISION.

PROGRAM-ID. DCNESAMP.

AUTHOR. IMA GATOR.

INSTALLATION. UF-NERDC, GAINESVILLE, FL.

*REMARKS.

* IBM VS COBOL II USING CICS COMMAND LEVEL INTERFACE

* PURPOSE: THIS TRANSACTION DISPLAYS SYSTEM INFORMATION

* AND LISTS THE LAST PFKEY THAT WAS ENTERED.

ENVIRONMENT DIVISION.

DATA DIVISION.

WORKING-STORAGE SECTION.

01 WS-CONSTANTS.

05 WS-PROGRAM-ID PIC X(08) VALUE 'DCNESAMP'.

05 WS-TRANS-ID PIC X(04) VALUE 'NESA'.

05 WS-MAP-NAME PIC X(08) VALUE 'DCNESAM '.

05 WS-MAPSET-NAME PIC X(08) VALUE 'DCNESAS '.

05 WS-COMMAREA-LENGTH PIC S9(04) COMP VALUE +8 .

05 WS-MESSAGE-LENGTH PIC S9(04) COMP VALUE +79.

05 WS-ERRMSG PIC X(40)

VALUE 'NESA TRANSACTION TERMINATED DUE TO ERROR'.

05 WS-ENDMSG PIC X(22)

VALUE 'NESA TRANSACTION ENDED'.

01 WS-COMMAREA.

05 WS-CA-PGMID PIC X(08) VALUE SPACES.

01 WS-SWITCHES.

05 WS-FIRST-TIME-SW PIC X(01) VALUE 'Y'.

88 FIRST-TIME VALUE 'Y'.

88 NOT-FIRST-TIME VALUE 'N'.

05 WS-RETURN-TO-TRAN-SW PIC X(01) VALUE 'Y'.

88 RETURN-TO-TRAN VALUE 'Y'.

88 END-TRAN VALUE 'N'.

01 WS-HOLD-AREAS.

05 WS-MESSAGE PIC X(79) VALUE SPACES.

05 WS-ABSTIME PIC S9(16) COMP.

05 WS-SYSDATE PIC X(08) VALUE SPACES.

05 WS-SYSTIME PIC X(08) VALUE SPACES.

05 WS-EIBDATE PIC 9(05) VALUE ZERO.

05 WS-RESP PIC S9(08) COMP VALUE ZERO.

COPY DFHAID.

COPY DCNESASD.

LINKAGE SECTION.

01 DFHCOMMAREA PIC X(08).

PROCEDURE DIVISION.

0000-PROGRAM-DCNESAMP.

PERFORM 1000-INITIALIZE.

IF NOT-FIRST-TIME

PERFORM 2000-RECEIVE-MAP.

PERFORM 3000-SEND-MAP.

IF RETURN-TO-TRAN

PERFORM 8000-RETURN

ELSE

PERFORM 9000-END-TRANSACTION.

GOBACK.

1000-INITIALIZE.

EXEC CICS HANDLE CONDITION

ERROR(9200-HANDLE-ERROR)

END-EXEC.

IF EIBCALEN = 0

MOVE LOW-VALUES TO DCNESAMO

MOVE WS-PROGRAM-ID TO WS-CA-PGMID

ELSE

IF EIBCALEN = WS-COMMAREA-LENGTH

MOVE 'N' TO WS-FIRST-TIME-SW

MOVE DFHCOMMAREA TO WS-COMMAREA

ELSE

PERFORM 9200-HANDLE-ERROR.

2000-RECEIVE-MAP.

MOVE LOW-VALUES TO DCNESAMI.

EXEC CICS RECEIVE MAP(WS-MAP-NAME)

MAPSET(WS-MAPSET-NAME)

INTO(DCNESAMI)

RESP(WS-RESP)

END-EXEC.

IF ENDI = 'END' OR 'end'

MOVE 'N' TO WS-RETURN-TO-TRAN-SW.

More...

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Cobol as the host language

In red, the CICS embedded commands

1. Mainframe Concept

Cobol CICS

3100-PROCESS-EIBAID.

IF EIBAID = DFHNULL MOVE 'NULL ' TO KEYO

ELSE IF EIBAID = DFHENTER MOVE 'ENTER' TO KEYO

ELSE IF EIBAID = DFHPA1 MOVE 'PA1 ' TO KEYO

ELSE IF EIBAID = DFHPA2 MOVE 'PA2 ' TO KEYO

ELSE IF EIBAID = DFHPA3 MOVE 'PA3 ' TO KEYO

ELSE IF EIBAID = DFHPF1 MOVE 'PF1 ' TO KEYO

ELSE IF EIBAID = DFHPF2 MOVE 'PF2 ' TO KEYO

ELSE MOVE 'OTHER' TO KEYO.

8000-RETURN.

EXEC CICS RETURN

TRANSID(WS-TRANS-ID)

COMMAREA(WS-COMMAREA)

LENGTH(WS-COMMAREA-LENGTH)

END-EXEC.

9000-END-TRANSACTION.

MOVE WS-ENDMSG TO WS-MESSAGE.

PERFORM 9900-TERMINATE.

9200-HANDLE-ERROR.

MOVE WS-ERRMSG TO WS-MESSAGE.

PERFORM 9900-TERMINATE.

9900-TERMINATE.

EXEC CICS SEND

FROM(WS-MESSAGE)

LENGTH(WS-MESSAGE-LENGTH)

ERASE

END-EXEC.

EXEC CICS SEND CONTROL

FREEKB

END-EXEC.

EXEC CICS RETURN

END-EXEC.

3000-SEND-MAP.

PERFORM 3100-PROCESS-EIBAID.

EXEC CICS ASKTIME

ABSTIME(WS-ABSTIME)

RESP(WS-RESP)

END-EXEC.

EXEC CICS FORMATTIME

ABSTIME(WS-ABSTIME)

MMDDYY(WS-SYSDATE)

DATESEP('/')

TIME(WS-SYSTIME)

TIMESEP(':')

RESP(WS-RESP)

END-EXEC.

MOVE WS-SYSDATE TO DATEO.

MOVE WS-SYSTIME TO TIMEO.

MOVE EIBDATE TO WS-EIBDATE.

MOVE WS-EIBDATE TO DATEJO.

MOVE EIBTRMID TO TERMIDO.

IF FIRST-TIME OR EIBAID = DFHCLEAR OR DFHCLRP

EXEC CICS SEND MAP(WS-MAP-NAME)

MAPSET(WS-MAPSET-NAME)

FROM(DCNESAMO)

ERASE FREEKB

END-EXEC

ELSE

EXEC CICS SEND MAP(WS-MAP-NAME)

MAPSET(WS-MAPSET-NAME)

FROM(DCNESAMO)

ERASEAUP FREEKB DATAONLY

END-EXEC.

That’s it

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1. Mainframe Concept

CSP

EZEM90 TEST

==>

ENTER = Continue PF3 = Exit

............................. FUNCTION SELECTION .............................

Enter application name =>

Enter function number => 2

1 Syntax check using the preprocessor

2 Run the application

Run Options

Trace => YES

Stop on statement count => 01000

Select statements to stop on => NO

Stop PF key =>

Initialization file (name) =>

Delayed preprocessing => YES

Change execution defaults => NO

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1. Mainframe Concept

Visual Age

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1. Mainframe Concept

Natural

0010 DEFINE DATA LOCAL

0030 1 #I (N4) INIT<-1>

0040 1 #TL-A (N3)

0050 1 #AX-A (N3)

0060 1 #TL-B (N3)

0070 1 #AX-B (N3)

0080 1 #FUNA (N5)

0090 1 #FUNB (N5)

0100 END-DEFINE

0120 SET KEY ALL

0140 INPUT USING MAP 'ZZDICOTO'

0160 INPUT USING MAP 'ZZDICOT3'

0180 IF #TL-A = 0

0190 REINPUT ' ENTER VALUE FOR A'

0200 END-IF

0210 IF #TL-B = 0

0220 REINPUT ' ENTER VALUE FOR B'

0230 END-IF

0250 #AX-A := #TL-A

0260 #AX-B := #TL-B

0270 INPUT NO ERASE 1/24 'THE FUCTION WILL BE X * X - 5'

0290 #FUNA := (#AX-A * #AX-A) - 5

0300 #FUNB := (#AX-B * #AX-B) - 5

0320 IF *PF-KEY = 'ENTR'

0330 INPUT USING MAP 'ZZDICOT2'

0340 IF (#FUNA * #FUNB) < 0 THEN

0350 INPUT NO ERASE 13/28 'THERE IS ROOT'

0360 ELSE

0370 INPUT NO ERASE 13/28 'THERE IS NO ROOT'

0380 END-IF

0390 END-IF

0410 END

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1. Mainframe Concept

A little bit easier to build the map…

Natural

Ob _ Ob D CLS ATT DEL CLS ATT DEL

. . T D Blnk T I ?

. . A D _ A I )

. . A N ª M D &

. . M I : O D +

. . O I (

. .

001 --010---+----+----+---030---+----+----+---050---+----+----+---070---+----

?NOME : (XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

?ENDERECO : (XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

?TELEFONE : (XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Enter-PF1---PF2---PF3---PF4---PF5---PF6---PF7---PF8---PF9---PF10--PF11--PF12---

Help Mset Exit Test Edit -- - + Full < > Let

NOME :

ENDERECO :

TELEFONE :

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2. Mainframe Users

  • 1. Mainframe concept

    • 1.1 In the sixties

    • 1.2 Suppliers

    • 1.3 Characteristics

  • 2. Mainframe users

  • 3. Mainframe legacy systems

    • 3.1 Some words about software assets

    • 3.2 Hardware and Software survival

    • 3.3 Application Software survival

    • 3.4 People

    • 3.5 Trends

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2. Mainframe Users

Who, since the 60’s, are the users?

Big companies: both government and private

Private : banks and most of the Top 500

Industries : (most of them migrated to SAP or other ERP systems)

Companies like that normally have a long life; most of them are alive today. Some solutions and processes they use were set long time ago.

The IT systems – software - is one of them.

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2. Mainframe Users

Note that it’s unlike a younger company, born in the 80’s or 90’s: in this case, the IT solutions and processes implemented were based on new designs, new architectures (web, for instance), new development environments.

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3. Mainframe Legacy Systems

  • 1. Mainframe concept

    • 1.1 In the sixties

    • 1.2 Suppliers

    • 1.3 Characteristics

  • 2. Mainframe users

  • 3. Mainframe legacy systems

    • 3.1 Some words about software assets

    • 3.2 Hardware and Software survival

    • 3.3 Application Software survival

    • 3.4 People

    • 3.5 Trends

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3. Mainframe Legacy Systems

3.1 Some words about the software assets

Let’s try to figure out the mainframe market, in Brazil, nowadays:

40 large or medium sized banks

50 government entities (both federal and state)

100 of the top 500 private Brazilian companies

 190 companies working with mainframe-based applications

(Worldwide = it’s a significant # of active mainframes)

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3. Mainframe Legacy Systems

Let’s try to figure out the size of the software assets of these companies (mainframe software):

(* = numbers based upon my experience)

Assuming :

a) 1000 LOCs / program average (*)

b) $125 / Function Point

(Capers Jones, SPR)

See http://www.boston-spin.org/slides/031-Oct02-talk.ppt

c) 1 FPs = 80 LOCs

(3rd generation language default, Caper Jones, SPR)

See http://www.spr.com/products/programming.shtm

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3. Mainframe Legacy Systems

The cost to change the application using new technologies, with new designs, is too expensive.

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3. Mainframe Legacy Systems

3.2 Hardware and Software survival

There’s a kind of “supplier commitment” to provide compatibility with previous versions (backward compatibility); there is no reason for great concerns about obsolete environments; programs “always” run on new equipment.

Hardware has the ability to run (host) many operating systems / virtual machines.

There is also the backward compatibility “commitment” with the base software (operating systems, compilers, dbms, etc.)

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3. Mainframe Legacy Systems

  • 3.3 Application Software survival - Reliability

  • It is well known that the more a software is tested, the more it is error-free and, thus, reliable.

  • Mainframe software technologies do not change substantially.

  • In the mainframe area, quickly releasing new products and new versions isn’t as fundamental as it is in the other platforms (remember: there is no competition…).

  • There is enough time to do the necessary tests.

  • The products are released in very reliable versions.

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3. Mainframe Legacy Systems

  • 3.3 Application Software survival - Reliability

  • Unavailability in a net PC and in a server supporting thousands of workstations is quite different.

  • Unscheduled boots rarely occur

  • There is a small number of interfacing components; to track and correct errors is easier

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3. Mainframe Legacy Systems

  • 3.4 Application Software survival - People

  • People who designed, developed, worked on the systems leave the company.

  • There’s a need to replace these technicians.

  • In Universities, there’s practically no more training on Mainframe technologies: CICS, Cobol, batch programming logic – for example, how to create a report, controlling lines, pages, breaks, etc? Do you know OOP? Forget it!

Legacy technologies in corporate environments – Alberto R. Schiesari – jan/2008

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3. Mainframe Legacy Systems

  • 3.4 Application Software survival - People

  • How do companies deal with this point?

    • Internal training

      Ex. 6 months programme with:

      Mainframe concepts

      Programming logic

      JCL and utilities

      Cobol

      PL/I

      CICS

      DB2

      TSO / Roscoe

    • Training suppliers

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3. Mainframe Legacy Systems

  • 3.5 Application Software survival – Trends

  • Batch applications:

  • They’ll probably continue the same way

  • I bet: 20 years from now you’ll see a batch system running in a quantum computer, “reading” 80 byte records as cards…

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3. Mainframe Legacy Systems

  • 3.5 Application Software survival – Trends

  • Online applications:

  • Break the application into layers

  • Change the application “foreground layer” (front end) by web based application

  • Leave the mainframe as a DB Server and “background layer” Server

  • Probably all terminal I/O operations migrating to the PC based applications

  • Probably all DB operations left in the mainframes

Legacy technologies in corporate environments – Alberto R. Schiesari – jan/2008

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Terminal input and output

Data validation; OK, demand services to Mainframe

CICS Data validation; CICS services;

demand services to DBMS

DBMS services, other file services

PC based

Mainframe

3. Mainframe Legacy Systems

3.5 Application Software survival – Trends

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Questions

Questions ?

Legacy technologies in corporate environments – Alberto R. Schiesari – jan/2008

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