Problem:
What are the SCH_validate errors that appear in the interbase.log file and what 
causes them.

Solution:
SCH_validate errors are internal server errors that are related to InterBase's
 internal scheduler.  When these errors occur the server is in a confused 
state and should be restarted.  

The SCH_validate errors are ususally accompanied by the InterBase server
 crashing.

The most common reason for these errors is due to faulty UDF programming.  
UDFs run in the InterBase server's memory space.  This makes it possible for
faulty UDFs to corrupt the server's memory space.

Verify the validity of all UDFs running on the server.  Make sure that they are coded 
correctly.

If the SCH_validate errors occur with no UDFs defined on any of the databases
contact InterBase Technical Services.