INTEC Department of Information Technology Evolution of Legacy Systems Strategic and managerial...
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Transcript of INTEC Department of Information Technology Evolution of Legacy Systems Strategic and managerial...
INTECDepartment of Information Technologyhttp://www.intec.rug.ac.be
Evolution ofEvolution of Legacy Systems Legacy Systems
Strategic and Strategic and managerialmanagerialissues based on a caseissues based on a case
Herman Tromp, Herman Tromp, Ghislain HoffmanGhislain Hoffman
ELISA workshop, Amsterdam, Sep. 23, 2003ELISA workshop, Amsterdam, Sep. 23, 2003
INTEC - Department of Information Technology
What is legacy What is legacy
Legacy : Money, etc. (to be) received by a person by the will of
and at the death of another person Something handed down from ancestors or
predecessors
(source : dictionary)
Legacy has a Positive connotation : value Negative connotation : old, out-of-date, inappropriate
for current use
INTEC - Department of Information Technology
What is a legacy system?What is a legacy system?
A legacy system is an operational system that has been designed, implemented and installed in a radically different environment than imposed by the current ICT strategy. It is also a system that still contains considerable business value and is critical for operations.
(Note : other definitions are available)
INTEC - Department of Information Technology
ContextContext
The ARRIBA project (see companion paper) Migration at LCM (this paper)
Largest organisation in Belgium, responsible for health care allowances (interfaces with government agencies, hospitals and indivual citizens in a variety of ways)
Large scale systems, parts of it about 30 years old “home developed” (no commercial software was
available then) Urgent need to migrate (hardware is becoming
obsolete) Objective of this paper : to discuss the strategic
and managerial issues of legacy migration
INTEC - Department of Information Technology
A few position statements ...A few position statements ...
... from the lessons learned Large scale systems can only be succesfully
migrated through evolution Evolution implies more than code refactoring (it
can hardly be refactored) Evolution must also consider architecture,
information models, persistency techniques, business culture, ...
... and thus has severe implications on strategy and management ...
... and is seriously impacted by these.
INTEC - Department of Information Technology
As is – What is “large scale”As is – What is “large scale”
0
100.000
200.000
300.000
400.000
500.000
600.000
700.000
1995 1996 1997 1998 1999 2000 2001
Average number of BS2000 transactions by day
INTEC - Department of Information Technology
As is – Numbers, numbers, numbersAs is – Numbers, numbers, numbers
0
50
100
150
200
250
300
1996 1997 1998 1999 2000 2001
Sequential passes per month.
INTEC - Department of Information Technology
As is – Numbers, numbers, numbersAs is – Numbers, numbers, numbers
System Subsystem Code # prog. # lines
Assurabilité Audit AA 5 8.321Assurabilité CRM AC 8 16.710Assurabilité AS 1094 1.213.254Assurabilité Divers AX 44 60.455Assurabilité Banque Carrefour CB 162 146.678Indemnités Audit UA 8 6.441Indemnités UK 450 473.835Intersoc PI 118 151.572Service social CS 196 248.740Soins de santé Fanchise CF 52 47.483Soins de santé ALC CR 71 96.036Soins de santé Audit GA 5 19.658Soins de santé Correcttion Val. GC 57 187.976Soins de santé Adm. Hospital. GH 243 360.862Soins de santé Accident GO 96 109.675Soins de santé Divers GX 157 191.815Soins de santé GZ 470 419.867Soins de santé Prestations à terme PT 230 244.307VHS PE 107 138.667Total 19 3573 4.142.352
INTEC - Department of Information Technology
Technical view on “as is”Technical view on “as is”
Four distinct types of processing:
1. Transactional, under control of a transaction monitor Many concurrent access points – ACID requirements imposed
by the transaction monitor 2. Batch or volume transactions
Single point of access – ACID requirements met by JCL scripts (experience based)
3. Sequential transactions The whole database is scanned - ACID requirements met by
running programs (experience based) 4. Journaling operations
Sequential copy of medical acts – no database involved All those manually scheduled depending on the time of
the day
INTEC - Department of Information Technology
Drivers for legacy evolutionDrivers for legacy evolution Redefinition of corporate strategy, e.g. from a data
processing model to a multichannel service oriented model
Business process redefinition and reorganisation, due to rapidly changing legal requirements
Cost of ownership of the current system (diversity of systems, corporate take-overs, software maintenance costs)
Lack of existence of a corporate information model Lack of a well defined architecture Outright end of life situation (no proper database system,
phasing out of a line of hardware and system software, etc…)
INTEC - Department of Information Technology
Specific drivers in the present caseSpecific drivers in the present case Predominance of COBOL code Business logic is hidden in JCL and in the heads
of the operators No database : data is stored in a flat file system... ... Which is a home-brewn version of an IDMS
database Data is stored in a single file and accessed
through a wrapper (its usage is obscured by the presence of multiple entry points)
The wrapper performs logical to physical mapping down to the disk block level, and is also responsible for hashing, garbage collection, etc.
INTEC - Department of Information Technology
Specific drivers in the present caseSpecific drivers in the present case Knowledge of business logic is present, but the
expertise on how to translate it into an implementation is getting lost (people are leaving)
“New” technologies are not very well understood, but experiments and POC’s are ongoing (but not in core operations) ERP EAI and message brokers Data warehousing J2EE based application servers RDBMS
(This seems to be a typical situation)
INTEC - Department of Information Technology
Evolving legacy systemsEvolving legacy systems
First option: rewrite from scratch (Big Bang) Second option: refactor (rewrite in new context) Third option: migrate (geriatric operation) Fourth option: reuse by trying to define
components Fifth option: a mix of the first four options
Evolution is the way to go ...
INTEC - Department of Information Technology
A management viewA management view
Motivation (why ?) Objectives (where ?) Basic postulates and constraints (environment) Critical success factors (how to measure
success) Risk assessment Methodology (how)
INTEC - Department of Information Technology
MotivationMotivation
LCM needs to make sure that it develops and maintains a strategic technology direction, keeps current with industry development, and employs the selected technologies appropriateto reach its long-term objectives: to be the leader in the healthcare and related social services.The strategic decision to start the REFAC project (Reorganisation of the Financial, Administrative and Control circuits) implies a complete revision of the “Health Care” information system. This revision is minimally based on the installation of a relational database. The IT Management considers this project to be an excellent opportunity to carry out the firststeps in leaving the current platform BS2000. However involving some risks, this migration operation appears to be essential andinevitable for the future. Movement to a new environment will reduce support requirements, enable faster responses to development needs, and permit staff to be reassigned to support emerging newtechnologies. Viewing data as an institutional asset will improve the quality of reports,allow LCM staff to respond easily to rapidly expanding requests for information, and provide a service oriented users environment.
INTEC - Department of Information Technology
ObjectivesObjectives
Set up a evolution plan from the BS2000 towards a new platform
Define a new technical infrastructure to be developed and installed
Create an efficient and flexible application and data architecture.
Accompany this with a budgetary, HRM and business reengineering plan.
Make the necessary budgets available
INTEC - Department of Information Technology
Postulates and constraintsPostulates and constraints
Migration by stages (no big bang) evolution Stage by stage synchronisation of data Definition of a corporate information model
accessible through a relational data base (Oracle 9x) Business Process Reengineering Real time system with availability 24x7 J2EE based thin client architecture via portal and
application servers No data replication (?) Interface with existing CRM and financial systems
INTEC - Department of Information Technology
Critical success factorsCritical success factors
Affordable but significant proof of concept Quick win definitions Succesful implementation of a strategic application
suite within 2 years Management and stakeholder support Support of users (business and regular)
INTEC - Department of Information Technology
Risk assesmentRisk assesment
Unfeasibility (technology mix, integration of COBOL/Java)
Complexity Performance (is already a problem) Obsolescence of techniques Lack of pragmatism Unmanageable systems (related to complexity) Cost control (hard ...) Lack of (human) resources
INTEC - Department of Information Technology
Methodolody and planningMethodolody and planning
Evaluation of the “as-is” situation (investigation of COBOL code, underlying data structures, ...)
Determine a “to-be” business and application architecture
Determine a “to-be” technical and deployment architecture
Evaluate evolution scenario’s between the “as-is” and “to-be” situation
Any methodology should reflect the structure of the organisation.
INTEC - Department of Information Technology
Conclusion ? Some empirical lawsConclusion ? Some empirical laws
“A system that is used will be changed “ (Lehman)
“An evolving system increases its complexity, unless work is done to reduce it” (Lehman)
“A system reflects the organisational structure that built it” (Conway)
“What applies to small systems does not apply to large ones” (DeRemer)
“Architecture wins over technology” (Morris-Ferguson)
INTEC - Department of Information Technology
Appendix – accessing informationAppendix – accessing information
Some extra information ...
INTEC - Department of Information Technology
Access Access
Actual access to applications
applications
MUT
LEASY
terminalsOpen
UTM
INTEC - Department of Information Technology
Future AccessFuture Access
Future access to applications
ApplicationsData interface
RDBMS
Terminals
Connector
Browser
Application Server
http-Server
PC
Browser
PC
InternetIntranet
JDBC
INTEC - Department of Information Technology
Handling data in COBOLHandling data in COBOLMONITOR
UserProgramma
SUB-Programma
FILE-HANDLER
M UT
FILE-HANDLER
LEASY
MUx
MUx
M08
POT
UID
VCS
VAKA
OONS
GIFT
- openen Leasy cata loog- openen files- openen transactie- in itia lisatie- oproepen FH L- oproepen user-program m a- s lu iten files
- business log ica- oproepen FH L- oproepen sub-program m a
- business log ica- oproepen FH L- oproepen sub-program m a
- lezen leden- om zetting fys-log - log-fys- wegschrijven leden
INTEC - Department of Information Technology
Data streamsData streams
Sequential Batch
Updates
Logging
- PPR --> BTM- USER --> BC- PRINT --> REMOTE
Read
OpenUtm
MUT
1200 seq
500 trx
300 BC160 BTM
5.700.000 leden
externe dataperformatie
INTEC - Department of Information Technology
Physical data organisationPhysical data organisation
RNR2r 1
RNM1x 2
RNR
20 %
Begin Vrije Ruim te
E inde fichier
E inde DATA
x RNM1 RNR1 2
s RNM RNR 4
r RNR2 1
RNR1RNM1
IND
DAT1 9...9
2 z
3 9...9
299 9...9
FSP
300 9...9
301 free end
15.000.000 recordsvan 1K (D AM -rcords)
13.125 records van 1 PP(PAM -pages = 2k )
13.125 records van 1 PP(PAM -pages = 2k )
y RNM RNR 2 HV 9...9
z RNM RNR 2 HV y
x
r
z
y
s
free
end
INTEC - Department of Information Technology
Example of a data structureExample of a data structure
ADM 01
BYD 03
ATT 04 DEL
BYD 05
MUT 02
E11 06
E11 09 E11 08 E11 07 PDL
XXX
INFO LID
- F IC N R- AD R ES- H V + FR EE Adres- LN G- R N R
- R N M- SW -SKIP- SEQ N R- U N IEK (adm _id)- D AT U M W ijzig
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000- LN G- N R- BAT C H -D AT- BAT C H - PR O G ID
- O N L-D AT- O N L-PR O G ID- O N L-PER SN R- D EL-PD L- SEQ N R
Record
1
Record
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