The data from the agent or the monitoring server can be
compressed before it is transmitted to the Warehouse Proxy Agent.
The data is then decompressed at the Warehouse Proxy Agent before
it is inserted in the warehouse database, allowing for efficient usage
of network bandwith between the historical client and the Warehouse
Proxy Server.
The following reductions can occur:
- A reduction in timeout errors due to a low bandwith between clients
and Warehouse Proxy Server. Timeout errors on the client side occur
when it takes more than 15 minutes for an export of data to complete
and be inserted in the warehouse database.
- A reduction in bandwith usage. Uploading historical data to the
warehouse can tie up a significant amount of bandwidth, and also impact
other critical applications sharing the network link.
- A reduction in the elapsed time for the upload over slow links.
Use this functionality when a slow network is used or when the
network is shared with other critical applications. However, compressing
the data does increase CPU usage, both at the agent where it is uploaded
and at the Warehouse Proxy Agent where it is decompressed. CPU costs
differently on a distributed source than on a z/OS® source. In a mixed environment, it is possible
to enable or disable the compression option (which is a server option),
depending on the source operating system of the client. It is also
possible to overwrite a server compression option.
Configuration parameters for the
Warehouse Proxy Agent are
set in the following files according to operating system:
- ITM_HOME\TMAITM6\khdenv
For example: C:\IBM\ITM\TMAITM6\khdenv
-
- ITM_HOME/config/hd.ini
For example: /opt/IBM/ITM/config/hd.ini
The Warehouse Proxy Agent configuration file now contains
two new variables that you can modify if necessary:
- KHD_SERVER_DIST_COMPRESSION_ENABLE
- If this variable is set to Y, then the Warehouse Proxy server
allows distributed clients to send compressed data. This variable
is set to Y by default.
- KHD_SERVER_Z_COMPRESSION_ENABLE
- If this variable is set to Y, then the Warehouse Proxy server
allows z/OS clients to send
compressed data. This variable is set to N by default.
The agent configuration file, if historical data stored at the Tivoli® Enterprise Monitoring
Agent, or the monitoring server configuration file, and if historical
data is stored at the monitoring server, accepts a new warehouse variable:
- KHD_CLIENT_COMPRESSION_ENABLE
- If set to N, and even if the Warehouse Proxy Agent server has
allowed the compression, the historical data is not compressed on
this source. This variable does not exist by default.
The new Warehouse Proxy Agent variables are visible
in a view in the configuration workspace of the Warehouse Proxy Agent.
They also exist on the configuration GUI of the Warehouse Proxy Agent.
You can see if the compression is occurring by using a tracing
level to see the data compressed at the client and uncompressed at
the server: ERROR (UNIT: khdxmts DETAIL) in the warehouse proxy agent.
To check uncompression in the server log file, see if the file contains
the following text:
khdxmts.cpp,154,"KHD_SendBuff_from_xmit_rep") Uncompressing the data
Use
ERROR (UNIT: khdxdacl DETAIL) to see the message about compression
in the client. To check that the client has overwritten the server
variable to not compress the data, see if the file contains the following
text:
khdxmts.cpp,167,"KHD_SendBuff_from_xmit_rep" Client did not compress the data
If compression has failed, you will see the following text in the
Warehouse Proxy Server log file,
khdxrpcs.cpp:
"Client compression failed, data was sent uncompressed"
If compression has failed, you will see the following text in the
client log file,
khdxdacl.cpp:
"Warehouse client unable to compress the data, data sent uncompressed"
If uncompression has failed, you will see the following text in
the Warehouse Proxy Server log file,
khdxrpcs.cpp:
"Uncompress error"
If uncompression has failed, you will see the following text in
the client log file,
khdxdacl.cpp:
"Warehouse client unable to compress the data, data sent uncompressed"
Complete the following steps to setup compression:
- Install or upgrade to the newest release.
- Configure the Warehouse Proxy Agent, using the GUI. The GUI can
pop up during install time, or can be launched by right clicking on
the warehouse Proxy entry in the manage Tivoli Monitoring Services panel. The new
server compression variables are part of the GUI and can be modified
as needed.
- Compression variables can also be reconfigured using the command-line
interface ( itmcmd config hd).
- Compression variables can also be reconfigured in the configuration
file itself. Configuration parameters for the Warehouse Proxy Agent are
set in the following files according to operating system:
- ITM_HOME\TMAITM6\khdenv
For example: C:\IBM\ITM\TMAITM6\khdenv
-
- ITM_HOME/config/hd.ini
For example: /opt/IBM/ITM/config/hd.ini
In mixed environments with a previous version of the client and
newer version of the server, or new version of the client and a previous
version of the server, the compression should not happen.