Guardian Procedure Calls Reference Manual

Figure 7 Exclusion and Access Mode Checking
• Applications with large receive-depth values
If you have applications that use large receive-depth values, you must periodically monitor
their Message Quick Cell (MQC) usage levels using the PEEK /CPU N/ MQCINFO command
processors to make sure that the total amount of memory allocated for MQCs does not approach
the per-processor memory limit for MQCs. This limit is 128 MB in H06.19/J06.08 and earlier
RVUs, and 1 GB in H06.20/J06.09 and later RVUs. For more information, see Table 54
(page 1580).
If you run applications with large receive-depth values on systems running H06.19/J06.08
or earlier RVUs, you should consider upgrading to H06.20/J06.09 or a later RVU if you
notice MQC memory usage levels approach the per-processor memory limit of 128 MB. To
determine the amount of memory used for MQCs by CPU N from the PEEK /CPU N/
MQCINFO command output, add the page counts for all the MQC sizes, and then multiply the
total page count allocated for MQCs by the page size (16 KB).
Disk File Considerations
• Maximum number of concurrent nowait operations
The maximum number of concurrent nowait operations permitted for an open of a disk file is
1. Attempting to open a disk file and specify a nowait-depth value greater than 1 causes
FILE_OPEN_ to fail with an error 28.
• Unstructured files
File pointers after an open
After a disk file is opened, the current-record and next-record pointers begin at a relative
byte address (RBA) of 0, and the first data transfer (unless positioning is performed) is
from that location. After a successful open, the pointers are:
◦
current-record pointer=0D
466 Guardian Procedure Calls (F)