0 - 2 of 2 tags for compression in teradata...

I am trying to compress a column databasename which is defined as CHAR(30).
As a limit specified by teradata that it can compress upto 255 values.
I had put the script as
COMPRESS ( .....255 values ....) ;

I am getting error as
5627:Column 'DATABASENAME' exceeds system limt for COMPRESS .

When I tried to reduce the columnvalues for compression.
When I specify 249 values It gets altered.For 250 to 255 values I get same error.

Also When I changed the column length to CHAR(40) to test.
It gets succeeded at 190 values .


I have compressed 55 tables and recovered 100 GB of space from the existing tables.My doubt is,

1) will compression affect the performance of the insertion,Updation and deletion of a table.

2) If it affects the performance means,then what is the usage of compression? (only for historical table?)