PERFORMING DOWNLOADS
Effect of Downloads on Existing Files and Data
VX 520 R
EFERENCE GUIDE 117
Optimize Available
Memory Space for
Successful
Downloads
One certificate file or signature file requires approximately 400 bytes of memory
space. The application designer must account for the extra memory required to
download and store these special files.
When planning your download procedure, carefully consider the total amount of
memory space required to store certificates and signature files and the application
files. In some cases, a considerable number of 400-byte signature files reside in
terminal memory at any given time. Here are some general guidelines to follow:
• Know the size of available memory (RAM and flash) of the receiving terminal;
also in back-to-back downloads, know the size of available memory on both
the sending and receiving terminals.
• Know in advance how application files are redirected to RAM or flash and to
file groups other than the target group.
• Defragment flash memory before performing a download to optimize the
available space in the flash file system.
• Before performing a download, use the Verix Terminal Manager menu
selections to clear the entire RAM and/or flash of a specific file group, as
necessary, to ensure proper use of available memory in the target group.
Support for File
Compression
For information regarding file compression, refer to the Verix V Operating System
Programmers Manual (VPN 23230).
Effect of
Downloads on
Existing Files
and Data
When downloading application files and data to a VX 520 terminal, an important
consideration is the effect of download procedure on existing application files, files
used in the file authentication process, and terminal configuration settings stored
in CONFIG.SYS files in the receiving terminal. Here are some important points:
• If a file already exists in the target file group, the existing file is replaced with
the new file of the same name. (Files in separate file groups can have identical
names).
• Always download executable files (and any other files to logically protect
under VeriShield file authentication) with the certificates and signature files
required to authenticate them.
• In full or partial application downloads, all CONFIG.SYS records on the
receiving terminal, both protected and non-protected (that is, beginning with *
or #), are retained. New CONFIG.SYS variables included in the download
package, including the *GO variable, selectively replace existing variables with
the same key name in the CONFIG.SYS file of the target group.
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