SQL/MP Installation and Management Guide

Managing Database Applications
HP NonStop SQL/MP Installation and Management Guide—523353-004
10-23
Using the COMPILE Option
Using the COMPILE Option
The COMPILE option influences the behavior of the SQL compiler. The option
determines which SQL statements are compiled during an explicit SQL compilation.
You can direct the SQL compiler to use the similarity check to determine if a
statement’s execution plan from a previous compilation is operable. The SQL compiler
then recompiles only the statements that fail the similarity check; the other SQL
statements retain their existing plans.
The COMPILE option has three forms:
•
COMPILE PROGRAM directs the SQL compiler to explicitly compile all SQL
statements in the program. COMPILE PROGRAM is the default.
If you include the STORE SIMILARITY INFO clause, the SQL compiler stores
similarity information for each SQL statement in the program file.
SQLCOMP
Option Behavior
CHECK INOPERABLE PLANS Option (continued)
RECOMPILE
(continued)
For an invalid dynamic SQL statement, the SQL executor performs the
similarity check as follows:
•
If the similarity check passes, the SQL executor executes the
statement without recompilation.
•
If the similarity check fails, the SQL executor recompiles (in
memory) and executes the statement using Guardian names and
DEFINE names as follows:
Uses names at prepare time if execution-time name resolution is
not enabled
Uses names at statement execution time if execution-time name
resolution is enabled
NORECOMPILE The SQL executor performs the similarity check for the invalid SQL
statement as follows:
•
If the similarity check passes, the SQL executor executes the
statement without recompilation.
•
If the similarity check fails, the behavior depends on the type of
statement:
•
For a static SQL statement, the SQL executor returns an error to
the program because of the NORECOMPILE option.
•
For a dynamic SQL statement, the SQL executor recompiles the
statement because the NORECOMPILE option has no effect on
dynamic SQL statements. Invalid dynamic plans are always
recompiled.
Table 10-2. Behavior of the SQL Executor for an Invalid Statement Detected After
Load Time (page 2 of 2)