Virtual Storage Requirements

Connect:Direct® for z/OS® executes with a REGION of 0 MB allocated for most environments. Using the default limits for the IEFUSI exit, IBM® Connect:Direct may have enough virtual storage both above and below the line to run many Processes concurrently. However, your results may vary depending on the data type, block sizes, compression, communication buffer sizes, and other factors. IBM Connect:Direct storage requirements also depend on the initialization parameters that you specify and the type of Process work being performed. In some cases, you may need to increase the size of the REGION or storage limits.

Note: Connect:Direct for z/OS may use above-the-bar storage. The in-storage trace table defaults to 2 MB above the bar storage, and is controlled by the TRACE.BUFFER initialization parameter. Each zFBA COPY step uses 32 MB of page-fixed above-the-bar storage for the duration of the step.

Specifying REGION=0M eliminates the need to determine the REGION needed, and does not use any more virtual storage than specifying just the needed amount.

The following initialization parameters affect storage allocation below and above the 16 MB line:

Parameters Description

MAXUSER (default 6)

MAXPRIMARY (default 6)

MAXSECONDARY (default 6)

MAXPROCESS (default 12)

These parameters determine the number of tasks that IBM Connect:Direct supports. Storage is obtained during initialization and remains for the duration of the JOB or started task. For each task, approximately 2 KB is allocated above the line and 1 KB below the 16 MB line.
V2.BUFSIZE (default 32K,128K) The first positional parameter specifies the default maximum buffer size that IBM Connect:Direct uses for LU6.2 and TCP/IP data transmission. The default is 32K. (K means thousands of bytes.) The second positional parameter is used to alter the TCP/IP send and receive buffer sizes within TCP/IP.

In general terms, the second positional parameter should be at least the same and not less than the first parameter and should be big enough to handle the largest V2.BUFSIZE override from the netmap. A good common practice is to have the second parameter be a multiple of the first parameter and at least twice or more than the first parameter.

TCP (default NO) The TCP parameter affects the program storage required. This parameter allocates approximately 3280 KB above and 112 KB below the 16 MB line.
UDT (default NO) The UDT parameter requires 4 MB above the line. Each concurrent UDT process requires an additional 50 MB above the line.





These exits are loaded at initialization and reside below the 16 MB line. The default value for these parameters is no exit. Samples are provided and described in the IBM Connect:Direct for z/OS Administration Guide.
STAT.QUEUE.ELEMENTS (default 1500) Stat queue elements are 2 KB each and allocated above the 16 MB line.
MAXSTGIO (default 1M,1M) This parameter limits the amount of I/O buffers for each COPY. The I/O buffers are allocated above the 16 MB line.

The following example shows reasonable settings for these initialization parameters:

TRACE.BUFFER = 2 (default)