Database Reference
In-Depth Information
This implies that eliminating it should approximately halve the overall response time. The analysis also shows that
10,000 SQL statements like the following one were parsed and executed once:
SELECT pad FROM t WHERE val = 0
Since a constantly changing literal is used, shared cursors in the library cache cannot be reused. In other words,
every parse is a hard parse. Figure
12-1
shows a graphical representation of this processing.
Figure 12-1.
The processing performed by test case 1
■
Note
the processing shown in Figure
12-1
is later referred to as
test case 1
.
It goes without saying that such processing is inefficient. Refer to the section “Solving Parsing Problems” later in
this chapter for possible solutions to such a problem.
Long Parses
The following sections describe how to identify performance problems caused by long parses. However, active session
history isn't covered. The reason is quite simple: it's rare to see parse calls that take more than few seconds. As a
result, most of the time it isn't sensible to analyze such a problem through active session history. In any case, if you
