SetTnxNoSync: No disk access before a sync

Question

Hello,
I try to use Berkeley DB to store a lot of KV.The software must index a lot of data (put/get) and then wait for resquest from user (get) or new information for the index (put/get).
During the big indexing phase, It should be great if Berkeley DB add all data in memory (with cache) and write it manually on disk (with a sync()) from time to time.
So I was looking for a "setDeferredWrite" method like in Berkley DB Java Edition.
I found this post: Re: Where is the setDeferredWrite?
So I try to do "EnvironmentConfig.setTxnNoSync(true)" with:
envConfig_ = new EnvironmentConfig();
envConfig_.setAllowCreate(true);
envConfig_.setInitializeCache(true);
envConfig_.setTransactional(false);
envConfig_.setTxnNoSync(true);
But I get an error message for an invalid argument:
+ incompatible with existing environment+
createEnv: java.lang.IllegalArgumentException: Invalid argument
java.lang.IllegalArgumentException: Invalid argument
at com.sleepycat.db.internal.db_javaJNI.DbEnv_open(Native Method)
at com.sleepycat.db.internal.DbEnv.open(DbEnv.java:248)
at com.sleepycat.db.EnvironmentConfig.openEnvironment(EnvironmentConfig.java:830)
at com.sleepycat.db.Environment.<init>(Environment.java:30)
at person.Env.createEnv(Env.java:67)
at person.Main.main(Main.java:25)
1. Are there other config information to change?
2. With setCachesize and setTxnNoSync, BDB will put everything in cache memory (if enough) without writing on disk? Are there other fields to change to add a lot of data during big indexing phase very quickly?
Thanks a lot

Answer 1

Hi,
There are two main reasons Berkeley DB writes to disk, apart from maintaining transaction semantics:
1) If the cache becomes full, some of the cache content needs to be written to disk. You should ensure that your cache is large enough to hold all the pages being modified.
2) Berkeley DB writes log records, it keeps a buffer of those log records. Once the buffer is full, the log records are written to disk. You can alter the size of the log record buffer, thus altering how often it is written to disk in your situation. Do that using the [url http://download.oracle.com/docs/cd/E17076_02/html/java/com/sleepycat/db/EnvironmentConfig.html#setLogBufferSize(int)] EnvironmentConfig.setLogBufferSize  API.
Please let me know if the above two suggestions help.
Regards,
Alex Gorrod
Oracle Berkeley DB