CDR_NIFCOMPRESS Configuration Parameter

Specifies the level of compression the database server uses before sending data from the source database server to the target database server.

onconfig.std value
0
range of values
  • -1 specifies no compression
  • 0 specifies to compress only if the target server expects compression
  • 1 - 9 specifies increasing levels of compression
takes effect
When the database server is shut down and restarted or immediately after the cdr change onconfig command is used

The CDR_NIFCOMPRESS (network interface compression) configuration parameter specifies the level of compression that the database server uses before sending data from the source database server to the target database server. Network compression saves network bandwidth over slow links but uses more CPU to compress and decompress the data.

The values have the following meanings.
Value Meaning
-1 The source database server never compresses the data, regardless of whether or not the target site uses compression.
0 The source database server compresses the data only if the target database server expects compressed data.
1 The database server performs a minimum amount of compression.
9 The database server performs the maximum possible compression.

When Enterprise Replication is defined between two database servers, the CDR_NIFCOMPRESS values of the two servers are compared and changed to the higher compression values.

The compression values determine how much memory can be used to store information while compressing, as follows:

0 = no additional memory
1 = 128k + 1k    = 129k
2 = 128k + 2k    = 130k
...   
6 = 128k + 32k  = 160k
...   
8 = 128k + 128k = 256k
9 = 128k + 256k = 384k

Higher levels of CDR_NIFCOMPRESS cause greater compression.

Different sites can have different levels. For example, Figure 1 shows a set of three root servers connected with LAN and a nonroot server connected over a modem. The CDR_NIFCOMPRESS configuration parameter is set so that connections between A, B, and C use no compression. The connection from C to D uses level 6.
Figure 1. Database Servers with Different Compression Levels
begin figure description - This figure is described in the surrounding text - end figure description
Important: Do not disable NIF compression if the network link performs compression in hardware.

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