SYSDUMMY1 table is different from other catalog tables(read previous post). This table is resided in multiple table spaces like EBCDIC, Unicode and ASCII.
You can use any of these SYSDUMMYx tables when you need to write a query but the table reference does not matter. For example, when you want to retrieve the value of special registers, you can use a query that references a SYSDUMMYx table.
Each of these tables contains one row. The difference between the tables is that they each have a different encoding scheme, as shown in the following table:
Table 1. Encoding scheme of SYSDUMMYx tables
SYSIBM.SYSDUMMY1 ==>EBCDIC (Default table).
For those SQL statements and tools that use SYSDUMMYx, having a SYSDUMMYx table in each encoding scheme helps avoid conversions.
For example, suppose that your SQL statement references a SYSDUMMYx table that is in a different encoding scheme than other objects in the statement. DB2 treats this statement as one that references objects with different CCSIDs, and conversion is likely to occur. To avoid this situation, reference the SYSDUMMYx table that has the same encoding scheme as the other objects in your query.