I need explanation for below questions.
what is line sequential buffer length in informatica?
how integration service handles when allocated buffer is full?
Line sequential buffer length in informatica is a property of session which specifies the accepted length of bytes from an individual record of a flat file source. The default size is 1024 as can be seen in the attached screenshot.
To improve the performance of a session generally the size is decreased.
When the allocated buffer is full, the integration service stops the execution of the session and logs the error message in the session logs.
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I am currently playing around with outputting FP32 samples via the old MME API (waveOutXxx functions). The problem I've bumped into is that if I provide a buffer length that does not evenly divide the sample rate, certain audible clicks appear in the audio stream; when recorded, it looks like some of the samples are lost (I'm generating a sine wave for the test). Currently I am using the "magic" value of 2205 samples per buffer for 44100 sample rate.
The question is, does anybody know the reason for these dropouts and if there is some magic formula that provides a way to compute the "proper" buffer size?
Safe alignment of data buffers is the value of nBlockAlign of WAVEFORMATEX structure.
Software must process a multiple of nBlockAlign bytes of data at a
time. Data written to and read from a device must always start at the
beginning of a block. For example, it is illegal to start playback of
PCM data in the middle of a sample (that is, on a non-block-aligned
boundary).
For PCM formats this is the amount of bytes for single sample across all channels. Non-PCM formats have their own alignments, often equal to length of format-specific block, e.g. 20 ms.
Back in time when waveOutXxx was the primary API for audio, carrying over unaligned bytes was an unreasonable burden for the API and unneeded performance overhead. Right now this API is a compatibility layer on top of other audio APIs, and I suppose that unaligned bytes are just stripped to still play the rest of the content, which would otherwise be rejected in full due to this small glitch, which might be just a smaller and non-fatal caller's inaccuracy.
if you fill the audio buffer with sine sample and play it looped , very easily it will click , unless the buffer length is not a multiple of the frequence, as you said ... the audible click in fact is a discontinuity in the wave ...an advanced techinques is to fill the buffer dinamically , that is, you should set a callback notification while the buffer pointer advance and fill the buffer with appropriate data at appropriate offset. i would use a more large buffer as 2205 is too short to get an async notification , calculate data , and write the buffer ,all that while playing , but it would depend of cpu power
Hello fellow programmers.
I'm trying to dump the contents of the USN Journal of a NTFS partition using WinIoCtl functions. I have the *USN_JOURNAL_DATA* structure that tells me that it has a maximum size of 512 MB. I have compared that to what fsutil has to say about it and it's the same value.
Now I have to read each entry into a *USN_RECORD* structure. I do this in a for loop that starts at 0 and goes to the journal's maximum size in increments of 4096 (the cluster size).
I read each 4096 bytes in a buffer of the same size and read all the USN_RECORD structures from it.
Everything is going great, file names are correct, timestamps as well, reasons, everything, except I seem to be missing some recent records. I create a new file on the partition, I write something in it and then I delete the file. I run the app again and the record doesn't appear. I find that the record appears only if I keep reading beyond the journal's maximum size. How can that be?
At the moment I'm reading from the start of the Journal's data to the maximum size + the allocation delta (both are values stored in the *USN_JOURNAL_DATA* structure) which I don't believe it's correct and I'm having trouble finding thorough information related to this.
Can someone please explain this? Is there a buffer around the USN Journal that's similar to how the MFT works (meaning it's size halves when disk space is needed for other files)?
What am I doing wrong?
That's the expected behaviour, as documented:
MaximumSize
The target maximum size for the change journal, in bytes. The change journal can grow larger than this value, but it is then truncated at the next NTFS file system checkpoint to less than this value.
Instead of trying to predetermine the size, loop until you reach the end of the data.
If you are using the FSCTL_ENUM_USN_DATA control code, you have reached the end of the data when the error code from DeviceIoControl is ERROR_HANDLE_EOF.
If you are using the FSCTL_READ_USN_JOURNAL control code, you have reached the end of the data when the next USN returned by the driver (the DWORDLONG at the beginning of the output buffer) is the USN you requested (the value of StartUsn in the input buffer). You will need to set the input parameter BytesToWaitFor to zero, otherwise the driver will wait for the specified amount of new data to be added to the journal.
How can I calculate storage when FTPing to MainFrame? I was told LRECL will always remain '80'. Not sure how I can calculate PRI and SEC dynamically based on the file size...
QUOTE SITE LRECL=80 RECFM=FB CY PRI=100 SEC=100
If the site has SMS, you shouldn't need to, but if you need to calculate the number of tracks is the size of the file in bytes divided by 56,664, or the number of cylinders is the size of the file in bytes divided by 849,960. In either case, you would round up.
Unfortunately IBM's FTP server does not support the newer space allocation specifications in number of records (the JCL parameter AVGREC=U/M/K plus the record length as the first specification in the SPACE parameter).
However, there is an alternative, and that is to fall back on one of the lesser-used SPACE parameters - the blocksize specification. I will assume 3390 disk types for simplicity, and standard data sets.
For fixed-length records, you want to calculate the largest number that will fit in half a track (27994 bytes), because z/OS only supports block sizes up to 32760. Since you are dealing with 80-byte records, that number is 27290. Divide your file size by that number and that will give you the number of blocks. Then in a SITE server command, specify
SITE BLKSIZE=27920 LRECL=80 RECFM=FB BLOCKS=27920 PRI=calculated# SEC=a_little_extra
This is equivalent to SPACE=(27920,(calculated#,a_little_extra)).
z/OS space allocation calculates the number of tracks required and rounds up to the nearest track boundary.
For variable-length records, if your reading application can handle it, always use BLKSIZE=27994. The reason I have the warning about the reading application is that even today there are applications from ISVs that still have strange hard-coded maximum variable length blocks such as 12K.
If you are dealing with PDSEs, always use BLKSIZE=32760 for variable-length and the closest-to-32760 for fixed-length in your specification (32720 for FB/80), but calculate requirements based on BLKSIZE=4096. PDSEs are strange in their underlying layout; the physical records are 4096 bytes, which is because there is some linear data set VSAM code that handles the physical I/O.
Unix serial ports have a large output buffer. Write calls return immediately as long as there's space in the buffer. When there isn't enough space, a blocking write waits until the buffer is emptied to some low level.
In Windows 7 SP1, the built-in 16550 serial port behaves as if there's no output buffer. It seems writes block until the data is output from the port. If there is a buffer, it's even smaller than the 16 bytes set in Device Manager (in Advanced Settings for COM1). The SetupComm function lets me specify recommended sizes for input and output buffers. However, the output buffer size doesn't seem to change any behaviour, and GetCommProperties always sets the dwCurrentTxQueue field to zero. The only thing SetupComm can do is increasing the size of the input buffer.
The documentation for SetupComm specifically permits the device driver to ignore the requested values.
Your best bet is to use overlapped I/O and handle the buffering yourself.
I'm designing a system that will write time series data to a file. The data is blocks of 8 bytes divided into two 4 bytes parts, time and payload.
According to MSDN the WriteFile function is atomic ( http://msdn.microsoft.com/en-us/library/aa365747(VS.85).aspx ), if the data written is less than a sector in size.
Since the file will only contain these blocks (there is no "structure" of the file so it's not possible to reconstruct a damaged file), added one after each other, it's vital that the whole block, or nothing is written to the file at all times.
So the question is, have I understood it correctly that a writefile less than a sector in size is alway written completely to disk or not written at all, no matter what happens during the actual call to writefile ?
WriteFile is atomic as long as the write does not cross a sector boundary in the file. So if the sector size is 512 bytes, writing 20 bytes starting at file offset 0 will be atomic, but the same data written at file offset 500 will not be atomic. In your case the writes should be atomic, since the sector size should be a multiple of 8.
This MSDN blog has more information on how to do an atomic multi-sector write without using transacted NTFS.