On Mon, 13 Nov 2023 12:54:31 -0600, Jon Perryman wrote: > ... >> and probably has some effect on performance for QSAM. > >I'm guessing that performance benefit is insignificant. More important is the >adverse effect of buffering by BSAM / QSAM. It violates the UNIX standard of >concurrent writes to a file. Most people don't think about the impact of this >logic which says you have a file open 20 times, the records will be >interleaved according to the time the write occurred. Instead of immediately >adding each record, BSAM / QSAM buffering would delay adding the records to >the file causing them to be out of sequence. I simply can't see IBM enabling >BSAM / QSAM buffering that would confuse Unix programmers, but I could be >wrong. > I suppose part of the answer is here: <https://www.ibm.com/docs/en/zos/3.1.0?topic=processing-unix-files-access-method>
- The access method buffers writes beyond the buffering that your program sees. This means that after your program issues BSAM WRITE and CHECK, QSAM PUT with BUFNO=1 or a VSAM PUT, the data probably is not yet on the disk. If the file is not a FIFO, your program can issue the BSAM or QSAM SYNCDEV or CLOSE macro to force immediate writing. This interferes with good performance. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
