OnBar Parameter BAR_NB_XPORT_COUNT

The documentation is a little unclear on BAR_NB_XPORT_COUNT. Are these data buffers within the DB server or within the OnBar region? I assume these buffers are the same size as the database pages. What are some of you with good OnBar performance using as a value?? TIA Doug Agnew DBA Charlotte Pipe & Foundry dagnew@charlottepipe.com

Just a few hints about BAR_NB_XPORT_COUNT & BAR_NB_XPORT_SIZE. 1. The number of buffer allocated for sending data for a single onbar process to/from the storage manager. If you have 4 onbar process, you will have 4 * BAR_NB_XPORT_COUNT buffer allocated. 2. If you change BAR_NB_XPORT_SIZE at ALL previous backup, both logs and archives, are invalid. 3. Generally it is already set as large as possible. The XBSA spec states that this can be 1 byte less then 64KB. Informix set it to one database page less than 64KB. So for system with 2KB database page size this would be 31 (2KB*31=62KB). What these buffers do is hold the archive data for both informix and the storage manager. In an attempt to not bycopy data Informix allocates a set (the number determined by BAR_NB_XPORT_COUNT) of buffers that are filed by the kaio threads in the engine and the pointers to these buffers are passed to onbar. This means that the actual data in the buffer (which is sized by BAR_NB_XPORT_SIZE) is not moved. onbar takes this pointer and hands it directly to storage manager. Again the data never moves. While this single buffer is being passed to the storage manager, oninit is filling the other buffers (BAR_NB_XPORT_COUNT - 1) with data. This will ensure that when onbar request another buffer it is already filled with data. To view the status of these buffer you can use the command onstat -g stq. This will show you the buffer and if they are on the full size (engine has filled them with data) or the empty side (engine needs to fill the buffer with data). You should generally see one buffer missing of these queues and that is the buffer currently being processed by the storage manager. Hope this helps, ---jmiller Doug Agnew wrote: > The documentation is a little unclear on BAR_NB_XPORT_COUNT. Are these data > buffers within the DB server or within the OnBar region? I assume these > buffers are the same size as the database pages. What are some of you with > good OnBar performance using as a value?? > > TIA > > Doug Agnew > DBA > Charlotte Pipe & Foundry > dagnew@charlottepipe.com