MappedByteBuffer force does not write to disk

Thread view:

vissuyk@yahoo.com - 20 Jun 2007 04:32 GMT

Hi All,

I have been playing with MappedByteBuffer and file channels (NIO). I
have been to read a FileInputStream succesfully. When I then update
(using mappedbytebuffer.put(byte[]), it does write the update to disk.
Next time I restart the Java program and perform the read, it does not
have the update.

I did mappedbytebuffer.close but that did not help. Any tips are
appreciated. JDk = 1.5, OS = Linux 32 bit RHAT

Thanks

Vissu

Reply to this Message

vissuyk@yahoo.com - 20 Jun 2007 04:39 GMT

BTW, I have been able to read the updated date in memroy. When the
program terminated and retstarted the update is not seen which means
it was not persistent. I was under the assumption that when using
mapped byte buffer the OS automatically propagates the writes to disk.

I opened RandomAccessFile() in rw mode, then obtained filechannel from
it, then got hold of MappedByteBuffer by maping the length of the
file.

viss...@yahoo.com wrote:

> Hi All,
>
[quoted text clipped - 10 lines]
>
> Vissu

Reply to this Message

Esmond Pitt - 21 Jun 2007 02:21 GMT

> I have been playing with MappedByteBuffer and file channels (NIO). I
> have been to read a FileInputStream succesfully. When I then update
> (using mappedbytebuffer.put(byte[]), it does write the update to disk.

> Next time I restart the Java program and perform the read, it does not
> have the update.

I don't understand. These two statements are mutually contradictory. If
the update went to the disk, it would have been there next run. Is there
a 'not' missing somewhere.

Reply to this Message

vissuyk@yahoo.com - 21 Jun 2007 03:19 GMT

> viss...@yahoo.com wrote:
> > I have been playing with MappedByteBuffer and file channels (NIO). I
[quoted text clipped - 6 lines]
> the update went to the disk, it would have been there next run. Is there
> a 'not' missing somewhere.

OOPS, the updates DID NOT make it to the disk. However, once updated,
the updated values can be read from memory location.

Reply to this Message

Esmond Pitt - 22 Jun 2007 02:05 GMT

> OOPS, the updates DID NOT make it to the disk. However, once updated,
> the updated values can be read from memory location.

Of course. So you're saying you called MappedByteBuffer.force() and
nothing happened to the disk? and no exception was thrown?

Reply to this Message

vissuyk@yahoo.com - 25 Jun 2007 16:56 GMT

On Jun 21, 9:05 pm, Esmond Pitt <esmond.p...@nospam.bigpond.com>
wrote:

> viss...@yahoo.com wrote:
> > OOPS, the updates DID NOT make it to the disk. However, once updated,
> > the updated values can be read from memory location.
>
> Of course. So you're saying you called MappedByteBuffer.force() and
> nothing happened to the disk? and no exception was thrown?

Thats' right. Called force, then program terminates. Another program
starts and accesses the file and it sees old content - not the updated
content.

Reply to this Message

MappedByteBuffer force does not write to disk

Free Magazines