When setting 'DB2_COMPATIBILITY_VECTOR=ORA' in non-ora DB, the resulting string length is different.

when it's going to setup "db2set DB2_COMPATIBILITY_VECTOR=ORA"~

$ db2set DB2_COMPATIBILITY_VECTOR=ORA
$ db2stop force
03/27/2023 18:05:52     0   0   SQL1064N  DB2STOP processing was successful.
SQL1064N  DB2STOP processing was successful.
$ db2start
03/27/2023 18:06:00     0   0   SQL1063N  DB2START processing was successful.
SQL1063N  DB2START processing was successful.
$ db2 connect to sample1

  Database Connection Information

Database server        = DB2/LINUXX8664 11.5.5.0 <----
SQL authorization ID   = DB2INST1
Local database alias   = SAMPLE1

$ db2set -all
[i] DB2_COMPATIBILITY_VECTOR=ORA <-----
[i] DB2TRC_DEF_BUFFSIZE=1024M
[i] DB2COMM=TCPIP

$ db2 get db cfg for sample1

      Database Configuration for Database sample1

Database configuration release level                    = 0x1500
Database release level                                  = 0x1500

.....

Number compatibility                                    = OFF
Varchar2 compatibility                                  = OFF
Date compatibility                                      = OFF

$ db2 -tvf tab2
SELECT CASE WHEN SUBSTR(U.COL1,1,1)='F' THEN 'OUT' ELSE 'IN' END AS USER_TYPE, LENGTH(CASE WHEN SUBSTR(U.COL1,1,1)='F' THEN 'OUT' ELSE 'IN' END) AS VARCHAR_LENGTH, CASE WHEN SUBSTR(U.COL2,1,1)='F' THEN 'OUT' ELSE 'IN' END AS USER_TYPE, LENGTH(CASE WHEN SUBSTR(U.COL2,1,1)='F' THEN 'OUT' ELSE 'IN' END) AS CHAR_LENGTH FROM TESTTAB2 U WITH ur

USER_TYPE VARCHAR_LENGTH USER_TYPE CHAR_LENGTH
--------- -------------- --------- -----------
IN                     3 IN                  3 <-----
OUT                    3 OUT                 3

 2 record(s) selected.