limit keyword support in DB2 latest version
There was no change that I am aware of in Fixpack 5 to the requirement that the registry variable  DB2_COMPATIBILITY_VECTOR must be set to MYS for the ... LIMIT x OFFSET y functionality to work.  (Unsetting it in FP5 still results in an error if you try to use LIMIT / OFFSET).

You may want to look to see if DB2_COMPATIBILITY_VECTOR is set in the global registry.

Notice that running db2set alone does not show DB2_COMPATIBILITY_VECTOR:

$ db2set
DB2COMM=TCPIP
DB2AUTOSTART=YES


While running db2set -all does, since it's set at the global level:

$ db2set -all
[i] DB2COMM=TCPIP
[i] DB2AUTOSTART=YES
[g] DB2_COMPATIBILITY_VECTOR=MYS
[g] DB2SYSTEM=host1
[g] DB2INSTDEF=db2inst1