If you're an administrator for a Rational Synergy/Change installation that uses Informix and you haven't seen this technote: "Increase IBM Informix Dynamic Server 11.5 STACKSIZE parameter to prevent Informix crashes", then we STRONGLY suggest that you give it a read and implement the setting change it suggests.
Under certain circumstances, the default STACKSIZE for the Informix server is too small and can possibly lead to a stack overflow condition, which can bring the server offline. While the server can usually be brought back online without incident, in some cases it cannot and the server needs to be re-created from backups.
The tech note above suggests increasing STACKSIZE and restarting the Informix server to pro-actively prevent the stack overflow issue. If you're an admin for Rational Synergy or Rational Change, and use Informix as your back-end database, we highly encourage you to implement the changes addressed in this technote.