The blocksize parameter specifies the number of bytes per I/O operation for a dump device. By default, the dump and load commands choose the “best” block size for your operating system. Whenever possible, use these defaults.
You can use the blocksize = number_bytes option to override the default block size for a particular dump device. The block size must be at least one database page (2048 bytes) and must be an exact multiple of the database page size.
For UNIX systems, the block size specified on the load command is ignored. Backup Server uses the block size that was used to make the dump.