You need to upgrade your database to Version 12.4.3 or Version 12.5 before you can upgrade to Version 12.6. Sybase IQ 12.6 supports upgrading from Version 12.4.3 to Version 12.6.
If you are migrating from any Adaptive Server IQ or Sybase IQ release prior to Version 12.5, be sure to read the Release Bulletins for all interim versions for important migration information, as well as new features in those versions.