section 2: year 2000 storm shi-ming huang. references robert a. martin, 1997, “dealing with dates:...

Section 2: Year 2000 StSection 2: Year 2000 Storm orm

Shi-Ming Huang

ReferencesReferences Robert A. Martin, 1997, “Dealing with Dates: Solutions for the Year 2000”, IEE

E Computer, Vol. 30, No. 3, March 1997. Philip H. Newcomb and Melvin Scott, 1997, “Requirements for Advanced Year

2000 Maintenance Tools”, IEEE Computer, Vol. 30, No. 3, March 1997. The Year 2000 and 2-Digit Dates: A Guide for Planning and Implementation, I

BM Report GC28-1251-00, 1996; http://www.s390.ibm.com/stories/tran2000.html.

Federal Government Year 2000 Information Directory, http://www.itpolicy.gsa.gov/mks/yr2000/y201toc1.htm

The Year 2000 Information Center, http://www.year2000.com Mitre Y2K Home Page, http://www.mitre.org/research/y2k CA Discovery Home Page, http://www.cai.com/products/ca2000/2000menu.ht

m The Year 2000: A Practical Guide for Professionals and Business Managers, t

he British Computer Society, November 1996, ISBN 0 901865 974 Proposal Criteria for “Century Compliances”, GTE Technology & System, 199

6.

2.1 What is the Y2K problem? Representing the year as a two digit number, causing f

ailures in arithmetic, comparisons, sorting, and input/output to databases or files when manipulating date data

Using an incorrect algorithm to recognize leap years for years divisible by 400

Hardcoding “19” into software routines or using two-digit years with “99” and “00” as reserved values meaning “never delete this” or “this is a demonstration account,” respectively (sometimes called “magic numbers”)

System date data type that may roll over and fail due to the storage register filling up.

Hardware – Problem Identify A hardware timer is the key component in determinin

g the date and time to an operating system or application. The timer is initialized with a value, based on a time and date, and is incremented at a sub-second factor. This value is then converted, upon request, to a date and time, and returned back to the operating system or application. Depending on the size of this timer and the routines used to convert this timer value into a time and date, errors can result when the timer value represents a year value of 2000 or beyond.

Earlier systems did not contain an internal battery, so the time needed to be set during each power on/IPL (Initial Program Loading) sequence. Later systems included an internal battery, and were able to maintain the date and time across IPLs. Regardless of the method used, the date and time are accessible by the operating system and applications. However, when the date changes from 1999-December 31-to 2000-January-1 depending on how the timer is implemented, different results can be returned to the operating systems and applications.

Hardware – Problem Identify

Any hardware that contains a timer needs to ware the Y2K problem.For example: Mainframe, Midrange computer, Microcomputer, PC , Storage machine, Printer, Network Machine, Output Device, PBX, etc.

Hardware – Problem Scope

Hardware – Problem Testing

The testing was focused on the hardware timers and associated firmware. Because of their age and lack of formal support, users must perform careful in-house testing well in advance of the year 2000.

Hardware – Problem Testing For Example: Personal computers (PCs) include read-only memory (ROM) software c

alled the basic input-output system (BIOS), which is responsible for basic boot functions and managing persistent data such as the date and time. Some Intel-based PC BIOS software do not correctly roll dates across the year 2000 boundary.

PCs maintain two dates: one date in the hardware internal clock called the real-time clock (RTC), and one in the operating system software (e.g., DOS or Windows). The date in the operating system software is created by converting the date in the internal clock.

The RTC is battery-supported (to maintain the date and time when the system is powered down); the RTC is also where the computer gets the date as it boots. Older Intel-based PCs have faults in their RTC that prevent them from rolling the century over properly. This improper date is then picked up by the operating system as the computer boots up, and is passed on to application programs when they call the operating system for the current date and time.

Hardware – Hardware – Case Study: TATUNG TCS-8950T Case Study: TATUNG TCS-8950T PCPC System Specification:

CPU: Intel 80386 OS: MS-DOS

Manufacturing Date: December, 1990

Manufacturer: Tatung CO., Taiwan

Hardware – Hardware – Case Study: TATUNG TCS-8950T Case Study: TATUNG TCS-8950T PCPC MS-DOS Date Screen

Hardware – Hardware – Case Study: TATUNG TCS-8950T Case Study: TATUNG TCS-8950T PCPC BIOS Setup Screen

Hardware –SolutionHardware –Solution Hardware issues are the most basic in that solving them depends on manufacturer support .

Software – Problem IdentifySoftware – Problem Identify The software can be classified into two types:

i.e. command-and-control system and information system. The main Y2K problems for both two types are the program code or data structure: Representing the year as a two-digit number; Using values such as 98, 99 and 00 as special fla

gs or hardcoding "19" into output routines; Failure to recognize 2000 as a leap year; Rollover of date data types stored as offsets from

a known date.

Software – Problem ScopeSoftware – Problem Scope Any software that does not pass the year 2000 com

pliance needs to ware the Y2K problem.

For Example: Languages and Compilers: such as Cobol, Fortran,

C, etc. Operating Systems: such as MVS, VM, OS/400, M

S-DOS, etc. Database Management Systems: DB2, IMS, SQL, e

tc. And more: such as Transaction Processing Systems,

EDI, Banking Systems, Spreadsheets, etc. .

Software – Problem TestingSoftware – Problem Testing The testing process involves date searching and impact analysis. For the first problem, date keywords are used, for which there is

considerable experience (see sample keyword lists). Most Common Date Keywords:

after, asof, as-of, before, begin, cal, calendar, ccyy, ccyymmdd, cen, century, clndr, cur, curr, current, cymd, date, day, days, dob, dt, dte, eff, effective, end, finish, first, fiscal, from, frm, fy, fye, greg, gregorian, horizon, jul, julian, last, leap, mdy, mmddyy, mmddyyyy, mo, modayr, mon, month, mos, mth, mm/dd/yy, m/d/y, m-d-y, post, roman, start, stop, sysdate, sysdte, through, thru, today, week, weeks, wk, wkly, wks, year, years, yr, yrs, yy, yyddd, ymd, yymmdd, yyyymmdd, yymmm, '00/00/00','12/31/99' ,'19','1999'

Impact analysis involves following data flow for inputs, parameters and constants to determine areas affected by potential non-compliant values.

Software – Case Study:CA-Impact/Software – Case Study:CA-Impact/20002000It is a powerful impact analysis tool that helps you determine

the impact and cost of converting applications to support the Year 2000. CA-Impact/2000 analyzes all of your COBOL programs and copybooks on a library-by-library basis, looking for fields that may contain dates.

Predefined date patterns identify the date fields in your program.

Software – Case Study:CA-Impact/Software – Case Study:CA-Impact/20002000

Once the date fields are detected, the Analyzer provides helpful analysis at various levels.

Software –SolutionSoftware –Solution There are at least seven major, viable courses of action, which c

an be combined as appropriate, to deal with an organization's Y2K problems: Expanding the year field to four digits: Encoding century information in a six-digit space Using a 100-year logic window Employing a data bridge that uses a logic window Reversing the system clock and using a 28-year time bridge Removing hardcoded values and use of special flags in date field

s Code all three leap year rules into programs Determine the span of time that date data types will work over an

d use them appropriately Replacing the system (including retiring it)

Software –Solution: Software –Solution: Expanding the Year Field to Four Expanding the Year Field to Four DigitsDigits This solution requires all references to and uses of a two-digit ye

ar format (YY) be converted to a four-digit year format(YYYY), and all programs must be converted to use the new format. The major risk in this approach is that a program may directly access the internal structures of a date field, thus changing the field size without also changing the logic accessing the internal structure will corrupt the revised system.

This solution is complete, and it ensures that your applications will operate correctly for the next 2,600 years. However, it involves modifying every program and every database that references date data; adjusting every positional reference to data fields; changing the format of every record that contains date data; and reformatting and rewriting every data file, including historic data files.

Software –Solution: Software –Solution: Expanding the Year Field to Four Expanding the Year Field to Four Digits Digits This approach may also require changing the format of message

s among systems, initiating a chain of changes that will require simultaneous testing and rollout of the new systems across organizations.

Software –Solution: Encoding CeSoftware –Solution: Encoding Century Information in Six Digits ntury Information in Six Digits There are at least five ways to do this: Encode full Julian Dates (the number of days elapsed since noon Januar

y 1, 4713 B.C.4 ) in a binary 48-bit field, allowing values for dates well beyond anything we should care to record (YYMMDD [left arrow] BBBBBB, B = 8-bit binary).

Use the two 8-bit YY fields to encode the full year in a binary 16-bit field, allowing values for the years of 216 -1=65,535 (YYMMDD [left arrow] BBMMDD, B = 8-bit binary).

Encode a century field (0 = 18, 1 = 19, 2 = 20, and so on) and replace the MMDD with a day-of-the-year field DDD (YYMMDD [left arrow] CYYDDD).

Encode a century field as above and encode the month as a character field (M*) with values 1-9, A, B, C representing the 12 months (YYMMDD [left arrow] CYYM*DD).

Encode the entire six-digit date field into an offset from 1 January 1900, which would also be good for the next 2,600 years (YYMMDD [left arrow] DDDDDD).

Software –Solution: Using Logic WiSoftware –Solution: Using Logic Windowsndows The sliding window technique uses a self-advancing,

100-year interval that generally crosses a century boundary. This technique determines the century of a 2-digit year by comparing the 2-digit year against a window of 100 years. The user specifies the number of years in the past and future relative to the system year. For example, if the range is 1 January 1954 through 31 December 2053, then YY greater than or equal 54 indicates 19YY otherwise YY less than or equal 53 indicates 20YY.

Software –Solution: Using Logic WiSoftware –Solution: Using Logic Windowsndows Advantages:

Requires changes to only programs Windowing is built into some programming langua

ges Disadvantages:

Considered a temporary solution Not applicable for organizations whose data span

more than 100 years Does not provide collating sequence support Does not provide indexing sequence support

COBOL Example with Language ECOBOL Example with Language Environment Sliding Windownvironment Sliding Window The first example illustrates using the Language Environment cen

tury window for a date in the future, a maturity date.

Call CEEDAYS to convert the MATURITY-DATE to an integer Lilian date

Call CEESCEN to set the century window to the current year Call CEEDATE to convert the Lilian to a character string with 4-di

git year

In this example, the maturity date 090425 (year 09, month 04, day 25) becomes 20090425 (year 2009, month 04, day 25).

COBOL Example with Language ECOBOL Example with Language Environment Sliding Windownvironment Sliding Window IDENTIFICATION DIVISION. PROGRAM-ID. FUTURE-DATE. DATA DIVISION. WORKING-STORAGE SECTION.* feedback code for callable service 01 FC PIC X(12).* parameter for CEESCEN 01 START-CW PIC 9(9) COMP.* parameters for CEEDAYS 01 MATURITY-DATE. 02 Y2 PIC 9(2). 02 M2 PIC 9(2). 02 D2 PIC 9(2). 01 PIC2STR. 02 PIC2STR-LENGTH PIC 9(2) COMP VALUE 6. 02 PIC2STR-STRING PIC X(6) VALUE "YYMMDD". 01 LILIAN PIC 9(9) COMP.

COBOL Example with Language ECOBOL Example with Language Environment Sliding Windownvironment Sliding Window * parameters for CEEDATE 01 NEW-DATE PIC X(80). 01 NMDATE REDEFINES NEW-DATE. 02 YYYY PIC 9(4). 02 MM PIC 9(2). 02 DD PIC 9(2). 02 FILLER PIC X(72). 01 PIC4STR. 02 PIC4STR-LENGTH PIC 9(2) COMP VALUE 8. 02 PIC4STR-STRING PICX(8) VALUE

"YYYYMMDD". PROCEDURE DIVISION.**************************************** set century window to start with the* current year (current system date)*************************************** MOVE 0 TO START-CW. CALL "CEESCEN" USING START-CW FC.******************************************** convert 2-digit maturity date year into* integer value to get a COBOL Lilian date******************************************* CALL "CEEDAYS" USING MATURITY-DATE, PIC2STR, LILIAN, FC.*************************************************** convert COBOL Lilian date into YYYYMMDD format************************************************** CALL "CEEDATE" USING LILIAN, PIC4STR, NEW-DATE, FC. END FUTURE-DATE.

Software –Solution: Employing a Software –Solution: Employing a Data Bridge Using a Logic WindoData Bridge Using a Logic Windoww This solution is very popular because: it allows for a fairly straightforward conversion of the

applications to a four-digit year, but; allows external interfaces to continue in two-digit

formats by having simple data bridges that map the internal and external date data through a logic window approach for all inputs and outputs.

Software –Solution: Software –Solution: Reversing the System Clock and Reversing the System Clock and

Using a 28-Year Time BridgeUsing a 28-Year Time Bridge For systems that no longer have the source code, cannot

recompile the source code, or have purchased components that are not century ready, there is an option other than replacement.

You can reverse the system clock by 28 years and write bridging scripts that add or subtract 28 years from the date data. The number is 28 because this offset retains the same days of the week and month. Adding 28 years to Saturday, 1 January 1972 will generate a new date of Saturday, 1 January 2000.

Note that this works only for periods that have a leap year every four years (1901-2100). So this approach is only good until 28 February 2100. .

Software –Solution: Software –Solution: Removing hardcoded values and Removing hardcoded values and use of special flags in date fieldsuse of special flags in date fields The problem comes from hardcoded values in software routines s

uch as "19" for the implied century and/or use of "99" and "00" as reserved values meaning "never delete this" or "this is a demonstration account," respectively (sometimes called "magic numbers") which limit the range of year values and may cause date comparisons to fail or pollute output values.

Other magic number dates include: 9/9/99, 99/99/99, 1/1/1, 1/1/11, 6/9/69, 6/7/89, 1/23/45, 6/6/66, 7/7/77, 8/8/88, and 12/31/99.

Software –Solution: Software –Solution: Calculating Leap Years CorrectlCalculating Leap Years Correctl

yy The three rules which the Gregorian calendar uses to determine leap year are as follows: 1.Years divisible by four are leap years, unless... 2.Years also divisible by 100 are not leap years, except... 3.Years divisible by 400 are leap years.

Therefore, the year 2000 is a leap year according to rule number three. The simple expression: if (year mod 4 == 0) && ((year mod 100 != 0) || (year mod 400 == 0)) {use 29 for days in February} else {use 28 for days in February}

The problem arises from difference between the internal representation and external representation. One common standard solution uses four digit years in the internal representation. This is okay for some purposes, but not all. For example, human interface may have been intended to be user friendly and supply the century, so that the actual input has just two digit years. The other issue is that the rest of the date fields (e.g., two digits for the month and the day in the month) may not be very convenient for doing the necessary operations. The whole eight digits also may not be very convenient for long-term storage. This of course is the Y2K problem.

Software –Solution: Determine tSoftware –Solution: Determine the span of time that date data tyhe span of time that date data types will work over and use them pes will work over and use them

appropriatelyappropriately The most interesting issue is date representation. There are enough ways to do this to make procedural issues seem straightforward. What is involved is satisfying some familiar "application constraints" in a way that supports all the ways of using the data. When changes for Y2K compatibility become the major consideration, this means some alternative representations have to be considered. The external representations are almost always strings, since human readability is usually an overriding issue. The internal representation is affected by tradeoffs in storage size and operational efficiency. The major alternatives to expanding the representation to four digit years in a string representation (already identified as the simplest approach) are:

Software –Solution: Determine tSoftware –Solution: Determine the span of time that date data tyhe span of time that date data types will work over and use them pes will work over and use them

appropriatelyappropriately using days (or sometimes seconds) from some carefully chosen base

using binary representations (e.g., of year, month, and day) in an easily accessed data structure (like a C++ date class),

treating the string representation as having packed digit component values rather than ASCII values (e.g., using packed decimal in COBOL and PL/I), so that more range can be encoded.

Software –Solution: Software –Solution: Replacing or Retiring the SysteReplacing or Retiring the Syste

mm For some systems, the best option may be to

replace them with Y2K-safe commercial products that do most of what you need. An interesting alternative to buying a commercial product is to merge with or buy a company that has Y2K-safe systems and retire your own.

The Methodology for the Year 2000 PrThe Methodology for the Year 2000 Problemoblem

Technical experts tend to talk about what changes are needed in how software handles and stores date data. Program managers tend to talk about planning, estimation, and inventory. Higher-level managers tend to talk about the cost and the diversion of resources. Each person struggling with the Y2K challenge tends to focus on that part of the solution uppermost in his or her mind.


A typical Y2K effort has six major phases. They are: Awareness Inventory Assessment and planning Renovation Validation Implementation

Awareness

Inventory

Assessment and planning

Renovation

Validation

Implementation


Methodology: Phase 1-AwarenessMethodology: Phase 1-Awareness Each organization must educate their people

about what the Y2K problem is and how to deal with it.

Many have a hard time believing that something as trivial as a lack of two digits in a date can cause a serious problem.

Methodology: Phase 2-InventoryMethodology: Phase 2-Inventory Scope the problem and lay out a high-level plan of activities. Inventory all systems and system components. Go beyond MIS

systems to identify all systems at risk. Do a high-level inventory of potentially affected code.

Make a estimate of cost. Use source lines of code totals for developed systems multiplied by industry cost factors to generate a quick estimate.

Refine the plan. Identify priorities, using disaster recovery plans to identify critical systems. Rewrite disaster recovery plans to reflect the Y2K problem and include safety consequences and secondary effects.

Methodology: Methodology: Phase 3-Assessment, and PlanningPhase 3-Assessment, and Planning

Conduct a detailed assessment of the portfolio, using a consistent definition of Y2K problems. For developed systems, use available tools, such as Impact

Analysis, Software Conversion (Figure) For purchased, interfacing, and other critical systems, use a

compliance questionnaire to interview the owners of the systems. The questionnaire is focused on establishing the types of issues that are, or are not, addressed by the other party (see Appendix).

Methodology: Methodology: Phase 3-Assessment, and PlanningPhase 3-Assessment, and Planning

Once you understand this, you can gauge the risk this poses to your systems and then decide whether you want to negotiate a fix or a replacement.

Identify potential solutions and their costs in dollars, schedule, and ripple effects.

Refine the plan and get upper management approval of plan and its schedule and cost estimates.

Make a full system backup of everything.

Analysis of Data Fields as GuideAnalysis of Data Fields as Guided by Century-Compliance Criterid by Century-Compliance Criteri

a. (GTE)a. (GTE)Is century represented

explicitly?

START ONLINE STORAGE Can century be inferred accurately?

Is policy to minimize changes to date

formats?

Is policy to make century explicit in all

date formats?

Must other fields in same record be

changed?

Is converting operational data to new format

practical?

Is format controlled by an industry standard or inter-

company agreement?

Is format shared by other software?

Can controlled format be changed before Y2K

deadline for field?

Can all software be changed before Y2K deadline for field?

Is value for century set or

used?Does field handle full range of values and special values (e.g.,

data edits?

Change format with temp bridge to non-compliant software

Y2K program

fails

Change logic to handle all valid values

No changes

No change to format. Change

logic to infer century.

No

Yes

Yes No

Yes No

No

Yes

Yes

No

YesNo

Yes

No

Yes

No

Yes No

No Yes

Yes No

No Yes

Is explicit century needed for file manipulations?

No

Yes

Change format to represent

century

Change logic to use century

ConvDisk.Fig

Methodology: Phase 4-RenovationMethodology: Phase 4-Renovation

Now you are ready to commence implementing fixes. Here you must define new and/or revised procedures and accompanying training, brief upper management on changes and revisions so that adjustments can be approved quickly, and use modern techniques to identify needed design changes.

Methodology: Phase 5-ValidationMethodology: Phase 5-Validation Testing against the century-compliance criteria falls into the

following three categories:1. General.

Some aspects of century compliance are independent of technology and application domain. For example, Jan. 1, 2000 follows Dec. 31, 1999 for all hardware and software.

2. Technology-specific. Some aspects of century compliance depend on the technology and the behaviors and features of that technology.

3. Domain-specific. Some aspects of century compliance depend on the requirements of a specific application. For example, the valid ranges for dates to be tested can vary with each application.

High-Level Guidelines for Test High-Level Guidelines for Test Cases in Y2K Test Procedures.Cases in Y2K Test Procedures.

Category Subcategory Guidelines

General Current date 1. Direct set, power-up roll-over2. Re-initialize from cold start3. Full date ranges

Calendar accuracy 1. Days of week in 2000 and 20012. Leap year in 20003. 366 days in 2000

Century ambiguity 1.High-risk values (1999-12-31, 1900-01-01, 2000-01-01, 2000-02-29)2.Ambiguous century in user interface3.Electronic interfaces (API such as O/S call for system date, etc.)

Technology-specific

Current date 1. Power-down continuity2. "System date" versus "current date"

High-Level Guidelines for Test High-Level Guidelines for Test Cases in Y2K Test Procedures.Cases in Y2K Test Procedures.

Category Subcategory Guidelines

Date representation 1.Overflow of base-and-offset representation2.Standards for Gregorian formats3.Century capability in storage and interfaces

Date manipulation 1.Date arithmetic2.Conversion between representations3.Sorting, searching, indexing4.Century designation available in storage and interfaces

Domain-specific

Century ambiguity 1.Accuracy in inferring century for each field in storage, user interface, and other interfaces.

Date representation 1.Industry standards and contract requirements2.Human-factors requirements3.Design and coding standards

Date manipulation 1.Access to archived data2.Manipulation of archived data3.Extended semantics

Methodology: Phase 6- ImplementaMethodology: Phase 6- Implementationtion

Here you field fixes, including training end users. While most organizations will be able to use their traditional methods for fielding new systems and upgrades for the changes needed for Y2K, there will probably be several additional issues that impact their traditional approach. The need to ensure that all changes are implemented on time against a firm, no-slip deadline, will be new for many organizations. The simultaneous changing of commercial components, developed components, and procedures will also be new for many. Finally, for those forced into a change in their interfaces, the coordination and simultaneous activation of your new release with your interfacing partners will be especially challenging when more than one interface is changing.

section 2: year 2000 storm shi-ming huang. references robert a. martin, 1997, “dealing with dates:...

Documents