Reference Guide

ZCOM Tables and Data Structures
Memory Organization
Chapter 3 39
Memory Organization
The ZCOM Logical Device Manager (LDM driver) reserves a contiguous
block of kernel memory for tables for its use. The maximum size of this
memory block is tunable at kernel build time through the
zcom_mem_size parameter in the “system” file used to build your
kernel. The default value for this parameter is 4 Mbytes. This memory is
allocated relative to a starting pointer. The memory is organized by
function into the following groups:
Figure 3-1 Memory Organization
The TTGEN configuration file describes the sizes and initial content of
these tables. When TTGEN is run, it produces a memory image file that
is the same size and in the same format as this memory layout. The
memory image file is loaded into the kernel memory by ZMON via the
LDM when the system is initialized. Most of the tables are preset up in
the file by TTGEN; however, the response headers, queue headers and
data buffers are created and initialized by the LDM.
Note that TTGEN reports the size of the memory block in the “System
Information” section of the listing (if a listing is requested). If the
tunable parameter zcom_mem_size is different from the reported size of
the memory block, the ‘ZCOM Data Buffers’ area will be increased or
reduced to fit the memory block in the kernel memory during ZCOM
subsystem startup.
ZCOM Header Structure
Node Table Entries
ZLU Tables
Logical Terminal Tables
Physical Terminal Tables
Interface Tables
Response Records
Queue Header Structures
ZCOM Data Buffers