40IBM Sterling Connect:Direct for i5/OS User’s Guide
Sterling Connect:Direct for i5/OS simulates block reads and writes. Using logical blocks instead of physical blocks, it allows you to modify the blocksize to match the other node in some cases.
Sterling Connect:Direct for i5/OS supports block mode transfer when the following conditions exist:
Remote node supports block mode
Source and destination files have like characteristics
Files are supported file types
Sterling Connect:Direct for i5/OS supports block mode transfers for the following i5/OS file types:
DB2 for i5/OS files (without staged compression)
Spool files
Save files
Stream files (using the integrated file system)
Simulating Blocksizes
The simulated blocksize determines whether a block mode transfer occurs. If the block mode transfer does occur, the simulated blocksize is used for the transfer. The following rules determine what simulated blocksize Sterling Connect:Direct for i5/OS uses.
As the receiving node, Sterling Connect:Direct for i5/OS determines the simulated blocksize by these conditions in order of precedence:
Destination file blocksize specified on the request
Source file blocksize sent by the sending node in the COPY control block If neither condition exists, Sterling Connect:Direct uses the record mode.
As the sending node, Sterling Connect:Direct for i5/OS determines the simulated blocksize by these conditions in order of precedence:
Source file blocksize specified on the request
Destination file blocksize specified on the request
Calculated value*
*Largest multiple of record size less than some arbitrary value, such as 4096.
Block Mode Transfer Examples
The following block mode transfer examples include both sending and receiving examples.
CDRCV Example—Not Specifying Source File Blocksize
In the first example, the request does not specify the source file blocksize. In this scenario, the following occurs:
The Sterling Connect:Direct for i5/OS node sets the source file simulated blocksize to 3200 by using the destination file value.
The receiving Sterling Connect:Direct for i5/OS sets the destination file simulated blocksize to the value specified on the request.
