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From "John H. Embretsen (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-981) Errors in Tuning Guide's "Properties case study"
Date Tue, 14 Feb 2006 14:22:09 GMT
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  
 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 = 
cs.setString(1, "derby.storage.pageSize"); 
cs.setString(2, "32768"); 

=== 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

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