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From: "Raymond Raymond" <raymond_derby@hotmail.com>
To: derby-dev@db.apache.org
Subject: Two questions on derby checkpointing 
Date: Thu, 16 Feb 2006 00:48:11 -0400
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I have some questions about derby checkpointing. Someone can
help me to make it clear? ^_^.

1. I want to summarize what events will trigger a checkpoint?
On the derby website :
http://db.apache.org/derby/papers/logformats.html
I found such comments:
-------------------------------------------------------------------------------------------------------------------------------------------
With the default values, a new log file is created (this is known as log 
switch) when a log file grows beyond 1MB and a checkpoint happens when the 
amount of log written is 10MB or more from the last checkpoint.

RawStore exposes a checkpoint method which clients can call, or a checkpoint 
is taken automatically by the RawStore when:

1. The log file grows beyond a certain size (configurable, default 1MB)
2. RawStore is shutdown and a checkpoint hasn't been done "for a while"
3. RawStore is recovered and a checkpoint hasn't been done "for a while"
-------------------------------------------------------------------------------------------------------------------------------------------
I am no very clear about what " for a while " means in the second and the 
third comments.
I also want to know are there any other events will trigger a checkpoint 
besides these?


2. As what we discussed in the "incremental checkpointing issue" before,
I need to monitor the data reads and log writes, to gather some runtime
disk I/O information. So far, I found the basic classes to do data reads are 
:
org.apache.derby.impl.store.raw.data.RAFContainer.java
org.apache.derby.impl.store.raw.data.InputStreamContainer.java

the basic class to do log writes is :
org.apache.derby.impl.store.raw.log.LogAccessFile.java

Are there any other classes is involved in data reads and log writes 
directly?

Thanks.


Raymond

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