During a review of the bar_activity log which accompanies the onbar backup, one of the messages seen in the log says: 'The Storage Manager <SM name> CANNOT support long buffers.' (Where SMname is the name reference to the Storage Manager)
Onbar uses transfer buffers to move data to and from the database while using a storage manager. With the advent of larger memory block availability for many machine environments, Newer operating systems permit larger memory blocks for data movement. The transfer buffer size is determined by the onconfig parameter, BAR_XFER_BUF_SIZE. A larger Buffer size is sometimes used when it can improve the backup speed.
The size of the transfer block which is used for the data transfer to or from the backup device can vary. The configuration parameter BAR_XFER_BUF_SIZE is used to specify the size of the transfer buffer.
The default onconfig.std values for BAR_XFER_BUF_SIZE are:
- 31 if the page size is 2 KB (2*31=62 kb)
- 15 if the page size is 4 KB (4*15=60kb)
If the storage manager supports long transfer buffers:
- when the page size is 4 KB, the value can be 1 - 16383 pages
- when the page size is 2 KB, the value can be 1 - 32766 pages
If the storage manager does not support long transfer buffers:
- when the page size is 4 KB, the value can be 1 - 15 pages
- when the page size is 2 KB, the value can be 1 - 31 pages
If the message '... CANNOT support long buffers' is evident, the storage manager cannot handle long buffers. Consider modifying the BAR_XFER_BUF_SIZE to a lower value.
Tivoli Storage Manager (TSM) is able to handle long buffers, but it may be useful to limit the size of the transfer buffer. Set the IFX_BAR_NO_LONG_BUFFERS environment variable to prevent the size of transfer buffers from exceeding 64 KB when the BAR_XFER_BUF_SIZE configuration parameter is set to a long transfer buffer size value. (The XBSA standard requires the maximum transfer size to be under 64 kb).