BAR_XFER_BUF_SIZE configuration parameter

Use the BAR_XFER_BUF_SIZE configuration parameter to specify the size of each transfer buffer.

onconfig.std value
31 if the page size is 2 KB
15 if the page size is 4 KB
units
pages
range of values
For storage managers that support long transfer buffers:
  • 1 - 16383 pages when the page size is 4 KB
  • 1 - 32766 pages when the page size is 2 KB
For storage managers that do not support long transfer buffers:
  • 1 - 15 if the database server base page size is 4 KB
  • 1 - 31 if the database server base page size is 2 KB
takes effect
When ON-Bar starts
When you reset the value dynamically in your onconfig file by running the onmode -wf or equivalent SQL administration API command.

Usage

The database server passes the transfer buffer to ON-Bar and the storage manager.

The value of BAR_XFER_BUF_SIZE is in database server base page sizes. For Linux™, Solaris, and HP, the database server base page size is 2 KB; and for AIX®, Windows™, and Mac, the database server base page size is 4 KB. To calculate the size of the transfer buffer in a storage space or logical-log backup, multiply the value of the BAR_XFER_BUF_SIZE configuration parameter by the system page size, as shown in the following formula: 
one transfer buffer KB = BAR_XFER_BUF_SIZE * pagesize
You can determine the system page size by running the onstat -b command.

The maximum size of the transfer buffer for many storage managers is 64 KB. Spectrum Protect and Informix® Primary Storage Manager support long transfer buffer sizes of up to 65532 KB.

To calculate how much memory, in KB, the database server needs for each transfer buffer, use the following formula: 
memory KB = (BAR_XFER_BUF_SIZE * pagesize) + 500 bytes/1028

The extra 500 bytes is for system use. For example, if BAR_XFER_BUF_SIZE is 15, the transfer buffer can be 66,292 bytes, or 64.5 KB.

The number of transfer buffers per backup stream is specified by the value of the BAR_NB_XPORT_COUNT configuration parameter, and the number of parallel backup streams is specified by the BAR_MAX_BACKUP configuration parameter.

Restriction: You cannot change the buffer size between a backup and restore. The values of the AC_TAPEBLOCK and AC_LTAPEBLOCK configuration parameters must be the same value as the value of the BAR_XFER_BUF_SIZE configuration parameter was at the time of backup.

Example

For example, for a transfer buffer size of 128*2 KB (a value of 256 KB) on Linux™, specify: 

BAR_XFER_BUF_SIZE  128