Mirage instance of a database server

Abstract

Instances of a database server can be of two kinds, regular or mirage that respectively handle database requests in sessions behaving normally or abnormally, and based on changes in behavior, sessions are relocated therebetween. Behavior of sessions is evaluated based on statistics generated in processing requests in individual steps within one or more stages, such as parse stage. The evaluation may be automatically tuned by changing tests that are enabled based on priorities, changing thresholds within tests, changing whether sessions are evaluated together as a group, and changing periodicity of evaluation. Evaluation may be triggered by news of normal/abnormal activity in locations of sessions' origin. Mirage instances can be of multiple classes, execute in lower/higher capacity computers. Sessions may start in either kind of instance. Sessions may be relocated for reasons unrelated to maliciousness, such as excessive utilization of resources, excessive errors, or update of software of the database server.