DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

If you specify this option, the result table of the cursor is dynamic. It means that the size of
the result table is not fixed and it may change depending on the changes made against
rows in the underlying table after the cursor is opened. All inserts, updates, and deletes by
the same application processes through the cursor are immediately visible. Also all
positioned updates and deletes are immediately visible even before commit. And inserts
and updates and deletes by other applications are visible once committed. No temporary
result table is created for SENSITIVE DYNAMIC, since the FETCH statements are
executed against the base table.
► ASENSITIVE SCROLLABLE
You can use this option, when you let DB2 determine the sensitivity of the cursor. DB2
determines whether the cursor behaves as SENSITIVE DYNAMIC SCROLLABLE or
INSENSITIVE (STATIC) SCROLLABLE depending on the update ability of the associated
SELECT statement. ASENSITIVE CURSORS may then require TEMP database since
they can resolve to INSENSITIVE cursors, depending on the SELECT statement.
– The cursor behaves as an INSENSITIVE SCROLLABLE cursor, when the SELECT
statement is read-only and does not allow the cursor to be sensitive. In these cases,
access to the declared temporary table may be necessary.
– The cursor provides maximum sensitivity, which is SENSITIVE DYNAMIC
SCROLLABLE, when the cursor is not read-only.
It is suitable for client applications that do not care about whether or not the server
supports sensitivity.
Note: There is no DYNAMIC option for INSENSITIVE. The syntax is SENSITIVE
DYNAMIC SCROLLABLE cursor (the query cannot be read-only) or INSENSITIVE
SCROLLABLE cursor (the query can be anything, but a temp table may be required for
materialization).
The current conditions for read-only cursors are listed under Declare Cursor in Chapter 5
of DB2 UDB for z/OS Version 8 SQL Reference, SC18-7426-01. The READ ONLY and
FETCH ONLY clauses by themselves do not require a temporary data base.
FETCH statement
There is no new option in V8 to use dynamic scrollable cursors. All the positioning keywords
for fetch (NEXT, PRIOR, FIRST, LAST, CURRENT, BEFORE, AFTER, ABSOLUTE, and
RELATIVE) that were introduced in DB2 V7 to support static scrollable cursors are equally
relevant for dynamic scrollable cursors. However, there are some restrictions and
considerations about the FETCH statement. Figure 3-45 shows the FETCH syntax.
Chapter 3. SQL performance 95