iTP Active Transaction Pages (iTP ATP) Programmer's Guide

Installing and Running ATP
iTP Active Transaction Pages (iTP ATP) Programmer’s Guide—522292-002
2-12
ATP Environment Variables
ATP Environment Variables
You can specify any of the following ATP environment variables in your configuration
file:
ATP_COMPILED_PAGE_CACHE_SIZE
Use this variable to specify the maximum entries allowed in the cache where
atp.pway stores the compiled pages. ATP will not check the time stamp of a page
in the cache until the cache is full. Once the cache is full and a new page comes in,
atp.pway will check the time stamp and replace the least recently used (LRU) page
with the new page.
A larger number of entries means more memory may be consumed by the page
cache; a smaller number means the server must check the file’s time stamp and swap
the files more frequently once the cache becomes full. Therefore the best value
depends on system memory size and the total number and size of the application’s
pages.
ATP_COMPILED_PAGE_CACHE_SIZE accepts a value from 1 to 1024. The
minimum value (1) causes checking and swapping to be performed every time a new
page comes in. Although the maximum size is 1024, the runtime maximum size may
be smaller if the application has large source files in the cache.
If this environment variable is not used, a default value of 23 entries will be used.
ATP_PAGE_CACHE_SIZE
Use this variable to configure a web-page cache within atp.pway to improve
performance in situations where web pages are not changing very frequently. Pages
are retained in a local cache in parsed format. The value signifies a number of web
pages (the number of .atp pages to be retained in cache). ATP will not consult the
disk version of a page until the cache becomes full, or until the atp.pway process
has stopped or received a signal defined by the variable
ATP_PAGE_CACHE_SIGNAL.
The minimum value of ATP_PAGE_CACHE_SIZE is 0; the maximum value is
1024. The minimum value, 0, will disable the context cache mechanism and will
cause expensive construct and destruct operations for each request. The default value
for
ATP_PAGE_CACHE_SIZE is 20.
To determine the best value of ATP_PAGE_CACHE_SIZE for your needs, use a value
slightly greater than the number of frequently used root pages in your application.
(Do not count server-side includes, just the pages that call the includes.)
ATP_RESTART_PAGE
Use this variable to refresh a cached page after the page is accessed a specified
number of times. The default value is 50, which means that a page will be accessed
50 times before it is refreshed. A value of 0 means that the page will never be
refreshed.