Informix Experts

Informix and the Minguo “Y1C Problem”

The “Y1C Problem” affects Minguo dates, a calendar currently used in the Republic of China (Taiwan).  The issues are similar to those encountered in the Y2K Problem.

The Minguo calendar begins with year 1 in 1912, the year the Republic of China was founded.  Months and days in the Minguo calendar are the same as the Gregorian calendar.  2010 is year 99 of the Minguo calendar, and year 2011 will be year 100 - the year the Y1C problem is encountered. 

 The first Minguo century is from Minguo year 1 (1912) through 100 (2011) and the second Minguo century is from Minguo year 101 through 200.  The century part of the Minguo year refers to the digit in the hundreds numeric position, not the century the year belongs in (just as the year 2010 is in the 21^st century but the century part of the year 2010 is 20). 

 The Y1C problem in IDS has two issues:

1. Supporting 3 digit years in Minguo dates
2. Providing a means of determining the century for Minguo dates with 2 digit years

3 digit year support:

 Prior to a change made in October 2008, only 2 or 4 digit year formats were supported for Minguo years, e.g. DMY2/C1 and DMY4/C1.  The change added support for the DMY3/C1 format specifier.   The fix was implemented in versions 11.10xC3, 10.00xC10 and 11.50xC1.

Minguo support of the DBCENTURY environment variable

The second fix adds DBCENTURY support for Minguo years.  Previous to the fix (11.50xC7), DBCENTURY settings were ignored when formatting Minguo dates.  If you specified a 2 digit year in a Minguo date and formatted it to a 3 digit year, it would always have returned a year with the century digit set to 0.  With the fix, the century part of a 2 digit year formatted to 3 or 4 digit year will depend on the DBCENTURY setting.   

DBCENTURY settings and their meanings:

R – Current century - century from the current date

P – Past century       - century for the date earlier than current date

F – Future century   - century for the date later than current date

C – Closest century - century for date closest to current date

Some examples:

The following table demonstrates the results of formatting Minguo dates with 2 digit years into Minguo dates with 3 digit years with various DBCENTURY settings and current dates.  The “Current Date” column is the date the action occurs on.  

Environment variables (other than DBCENTURY):

                DB_LOCALE=zh_TW.big5

            CLIENT_LOCALE= zh_TW.big5

            DBDATE=MDY3/C1

 Without the fix, the 3 digit formatted dates would all have had a 0 in the century (100’s) place.  Note that if a -1 century would be returned, we will return a 0 instead since there is no -1 century in the Minguo calendar.

 Minguo DBCENTURY support is included in 11.50xC7.

Example of use:

Create the following two files, then run test.sh. 

 Test.sh:

            #!/bin/sh

if [ "x$INFORMIXSERVER" = x ]; then

      echo This file must be run from within an IDS environment

      exit 1

fi

export DB_LOCALE=zh_TW.big5

export CLIENT_LOCALE=zh_TW.big5

export DBDATE=MDY3/C1

export DBCENTURY=R

cat minguo.sql | dbaccess - -

export DBCENTURY=P

cat minguo.sql | dbaccess - -

export DBCENTURY=F

cat minguo.sql | dbaccess - -

export DBCENTURY=C

cat minguo.sql | dbaccess - -

minguo.sql:

drop database zhtw;

create database zhtw;

create table t1(c1 date);

insert into t1 values('08/08/99');

insert into t1 values('08/08/02');

insert into t1 values('080848') ;

insert into t1 values('080852') ;

select * from t1;

The value of locale variable, CLIENT_LOCALE or DB_LOCALE can be broken into 4 parts.

     1          2                   3                      4    
<language>_<territory>.<Code set name/Code set number>[@modifier]
       --------   --------    -----------------------------   --------

ll ............ represents the Language


tt ........... represents the Territory, or cultural convention.


xxxx ....... represents the Code set Name or the Code set Number supported by the locale and


xyz ......... represents the Modifier. This is the only optional part in a locale value.



The modifier, sometimes refered as variant, modifies the cultural-convention settings that the language and territory settings imply. It usually indicates a special localized collating order that the locale supports.

CLIENT_LOCALE = de_at.cp1252@euro, and
CLIENT_LOCALE = de_at.1252@euro


• Here, both CLIENT_LOCALE values represent the same locale.




• 1252 is the Code set number for Code set name, cp1252. We can specify either Code set name or the Code set number in a locale value.

where,

- de ........... represents the German language
- at ............ the territory, Austria
- cp1252 ... the code set used for the encoding and
- euro ....... the modifier used for the locale



So, this is German language locale, for Austria, using cp1252 encoding and euro modifier.

Now, to check if this locale file exists, where to lookup ?

All locale files reside under directory $INFORMIXDIR/gls/lc11

To lookup for locale files for language (ll) and territory (tt), we check under $INFORMIXDIR/gls/lc11/ll_tt directory.




In our example, to lookup for locale files for German language (de), for territory Austria (at), we will lookup $INFORMIXDIR/gls/lc11/de_at directory

Next, under the specified locale directory, look for files with name represented by hex value of the code set name/ code set number, along with modifier name if modifier is specified, with an extension .lco



In our example, hex value for Code set cp1252 is 04e4 and modifier euro is used. So, we will look for file 04e4euro.loc under directory $INFORMIXDIR/gls/lc11/de_at.

How and where to find the hex value for a Code set name ?

For any Code set name, its Code set number and hex value can be looked-up in file $INFORMIXDIR/gls/cm3/registry.

Example:

Let us find the hex value for Code set name Latin-3.

We can find the information in file

$INFORMIXDIR/gls/cm3/registry



  In the registry file ...

- first coulmn represents the code set name,
- second column is code set number
- third column is the hex value of the code set number, and
- fourth column, is either blank or has comment about the code set.



Let us lookup for code set, Latin-3 in registry file and see what we find.
We get the following value.





   Latin-3          57346              0xe002  					
  ---------      ------------	      -----------     --------------------------------
 code set name   code set number     hex value      in this case, there is no comment 

NOTE:

• Locale values are case in-sensitive.




Example:

DB_LOCALE = de_de.cp1252, DB_LOCALE = de_de.CP1252.
Here, both locale values are valid, representing the same code set.




• You can specify either code set name or code set number in a locale value, but you cannot use the hex value of the code set number.


Example:

DB_LOCALE = fr_ca.57372 or fr_ca.utf8, ........ both values are valid and they represent the same code set.


DB_LOCALE = de_de.cp1252 or de_de.1252 .... both values are valid and they represent the same code set


DB_LOCALE = de_de.04e4 ............... this in invalid. Code set's hex value cannot be used in a locale value.




• If modifier is not specified in the locale variable, like say ...

CLIENT_LOCALE = de_at.cp1252


- to locate the locale file, look for .loc under the language_territory directory. In this case, we look for following file ...

$INFORMIXDIR/gls/lc11/de_at/04e4.lco




• If modifier is specified in the locale variable, like ...

CLIENT_LOCALE = de_at.cp1252@euro




- to locate the locale file, look for .lco file under language_territory directory. In this case, we look for following file ...

$INFORMIXDIR/gls/lc11/04e4euro.lco




• Code set name, its corresponding Code set number and hex value is specified in file
  $INFORMIXDIR/gls/cm3/registry.
  
  
• Locale Territory/ Country code and Language code can be looked up in file
  $ILS_INSTALL_DIR/release/GLS_INFO
  
  
  
  
• Conventionally, for LOCALE variable having value ll_tt.xxxx[@xyz], following locale file should exist.
$INFORMIXDIR/gls/lc11/ll_tt/<hex value of xxxx>[xyz].lco




Seema Kumari
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