Errors in Tuning Guide's "Properties case study"
------------------------------------------------
Key: DERBY-981
URL: http://issues.apache.org/jira/browse/DERBY-981
Project: Derby
Type: Bug
Components: Documentation
Versions: 10.0.2.1, 10.1.1.0, 10.1.1.1, 10.0.2.0, 10.2.0.0, 10.1.2.2,
10.1.2.1, 10.1.2.0, 10.1.1.2
Environment: All
Reporter: John H. Embretsen
Assigned to: John H. Embretsen
Priority: Minor
The tuning guide contains a "Properties case study", demonstrating precedence
and persistence of derby properties; see
http://db.apache.org/derby/docs/dev/tuning/ctunsetprop32443.html. There is at
least one factual error and a couple of inaccurate details in this case study:
1) The value of the property derby.storage.pageSize that is being used in the
last example should be 32768, not 8192:
After the example statement
CREATE TABLE table4 (a INT, b VARCHAR(10))
the case study states
"Derby uses the persistent database-wide property of 8192 for this table, since
the database-wide property set in the previous session is persistent and
overrides the system-wide property set in the derby.properties file."
In the previous session, however, the database-wide property
derby.storage.pageSize is set to 32768 (not 8192), by doing the following:
=== start quote ===
You establish a connection to the database and set the value of the page size
for all new tables to 32768 as a database-wide property:
CallableStatement cs =
conn.prepareCall("CALL SYSCS_UTIL.SYSCS_SET_DATABASE_PROPERTY(?, ?)");
cs.setString(1, "derby.storage.pageSize");
cs.setString(2, "32768");
cs.execute();
cs.close();
=== end quote ===
8192 is the value that is specified in the derby.properties file, which is
overridden by the value (32768) specified in the database.
(Assuming that the same database is being used).
2) Inconsistent use of application name:
The case study describes persistence/precedence of a derby property by showing
different ways of specifying this property when starting/running an application
(embedded Derby). It seems that the intention was to show this using the same
application and database. However, different application names are used
throughout the case study:
a) java -Dderby.system.home=c:\system_directory MyApp
b) java -Dderby.system.home=c:\system_directory -Dderby.storage.pageSize=4096
myApp
c) java -Dderby.system.home=c:\system_directory myApplication
Potential confusion may be avoided by using the same application name
throughout the case study.
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