Auxiliary scan descriptors required: N
When a query involving referential integrity requires a large number of user or system tables, including references to other tables to check referential integrity, this showplan message indicates the number of auxiliary scan descriptors needed for the query. If a query does not exceed the number of pre allocated scan descriptors allotted for the session, the “Auxiliary scan descriptors required” message is not printed.
The following example shows partial output for a delete from the employees table, which is referenced by 30 foreign tables:
delete employees where empl_id = "222-09-3482"
QUERY PLAN FOR STATEMENT 1 (at line 1).
Auxiliary scan descriptors required: 4
STEP 1
The type of query is DELETE.
The update mode is direct.
FROM TABLE
employees
Nested iteration.
Using Clustered Index.
Index : employees_empl_i_10080066222
Forward scan.
Positioning by key.
Keys are:
empl_id ASC
Using I/O Size 2 Kbytes for index leaf pages.
With LRU Buffer Replacement Strategy for index leaf pages.
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
FROM TABLE
benefits
Index : empl_id_ix
Forward scan.
Positioning by key.
Index contains all needed columns. Base table will not be read.
Keys are:
empl_id ASC
Using I/O Size 2 Kbytes for index leaf pages.
With LRU Buffer Replacement Strategy for index leaf pages.
.
.
.
FROM TABLE
dependents
Index : empl_id_ix
Forward scan.
Positioning by key.
Index contains all needed columns. Base table will not be read.
Keys are:
empl_id ASC
Using I/O Size 2 Kbytes for index leaf pages.
With LRU Buffer Replacement Strategy for index leaf pages.
TO TABLE
employees
