Updating Data In Oracle 8i

Yes, this is possible, most likely in one SQL statement.  To preserve the "filename.ext" portion of the data in col2 and col3 you need to use a combination of operators:
instr, substr and the concatenation operator (||).

I'm assuming that the data in col2 and col3 varies in length from record to record.  If it is all the same it is easier, just count the characters and hard-code the first argument for "substr".

You need "instr" to find the position of the last "/" character in data.  By default, "instr" starts at the beginning of a string and counts forward, but if you supply a negative argument for "instr", it starts at the end of the string, so this will find the last position of "/":
instr(col2,'/',-1)

You need to use "substr" to get the filename and ext starting one position after the position that "instr" found, so your update statement for clo2 will look something like this:
update [table_name]
set col2 = [new server] || substr(col2,instr(col2,'/',-1) +1)

You don't need to specify the third parameter for "substr", it will default to the length it finds to the right of its start position that you found with "instr".

You can also combine the updates for col1 and col3 into one SQL statement that will do all of the updates at one time (assuming that you want all rows treated the same way).

Previous comment did not appear.  Trying again.

1. Single Oracle table.
2. Columns look like this:

COL1 = OBJECT_TYPE         VARCHAR2(25)
COL2 = TEXT_DATA           LONG
COL3 = ORACLE_TEXT_DATA    VARCHAR2(2000)

3. COL1 is search and replace.  All 'ABC' found get replaced with 'DEF'.

4. COL3 is search and add prefix. Current data is UNC path (i.e. \\SERVERNAME\SHARE\FILENAME.EXT)  I need to replace the UNC with a URL, but keep the file name intact.

So, '\\SERVERNAME\SHARE\' becomes 'http://SERVERNAME/VIRTUALDIRECTORY/' and the output in the updated row is:

http://SERVERNAME/VIRTUALDIRECTORY/FILENAME.TXT

Hope this clears up what we're after.  If not let me know.  

Well experts, there seems to be an easier way.  Apparently Oracle has a 'REPLACE' function that is designed for cases such as mine.

For example:

UPDATE tablename
SET
col1 = 'DEF',
col3 = REPLACE(REPLACE('http://newserver/vdirectory/'||REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(LOWER(ORACLE_TEXT_DATA), '\', '/'), 'http://oldserver/', ''), '//oldserver/', ''), '/oldserver/',''), 'oldserver/', ''), 'http://newserver/vdirectory/http://', 'http://'), 'http://newserver/vdirectory/www.','http://www.')

WHERE
col1 Like '%ABC%' Or
col1 Like '%XYZ%'

Note the idea is to find oldserver and replace it with newserver/vdirectory. The additional replace function calls are to ensure that the final output is of the format http://newserver/vdirectory/rest of old link here for all the updated records. The cool thing is, all links without reference to oldserver will remain unchanged.

While the substr instr and concat operator may work...they are a bit clumsy and hard to get correct.  The REPLACE function *IS* the answer.