Specifies the percent of hard disk I/Os allowed during the execution of a statement that includes a query involving hash algorithms, before the statement is rolled back and an error message is reported.
Option can be set at the database (PUBLIC) or user level. When set at the database level, the value becomes the default for any new user, but has no impact on existing users. When set at the user level, overrides the PUBLIC value for that user only. No system privilege is required to set option for self. System privilege is required to set at database level or at user level for any user other than self.
Requires the SET ANY PUBLIC OPTION system privilege to set this option. Can be set temporary for an individual connection or for the PUBLIC role. Takes effect immediately.
If a query that uses hash algorithms causes an excessive number of hard disk I/Os (paging buffers from memory to disk), query performance is negatively affected, and server performance might also be affected. HASH_THRASHING_PERCENT controls the percentage of hard disk I/Os allowed before the statement is rolled back and an error message is returned. The text of the error message is either Hash insert thrashing detected or Hash find thrashing detected.
The default value of HASH_THRASHING_PERCENT is 10%. Increasing this value permits more paging to disk before a rollback and decreasing this value permits less paging before a rollback.