- How does one start and stop the Oracle Web Listener?
Answer:
V1:wlctlstart ‹ port_number ›eg.wlctlstart 8888
wlctlstop ‹ port_number ›
V2.0: wlctl2 start ‹ listener_name › eg.wlctl2 start admin
wlctl2 stop ‹ listener_name ›
V2.1: wlctl21 start ‹ listener_name › eg.wlctl21 start admin
wlctl21 stop ‹ listener_name ›
- How does one program using the PL/SQL Web Agent?
Answer:
The Oracle Web Agent extends the Common Gateway Interface (CGI) to Oracle PL/SQL stored procedures.Programming is done in PL/SQL using the following set of packaged procedures:
- HTP - Hypertext Procedures
- HTF - Hypertext Functions
- OWA_UTIL - Oracle Web Agent Utilities
Example PL/SQL procedure:
CREATE OR REPLACE PROCEDURE HelloWorld AS
BEGIN
htp.htitle('My first dynamic Web page');
htp.print('Hello world');
htp.line;
END HelloWorld;
/
To run this example you would typically provide an URL like this to your Web Browser:
http://your.host.name/oracle_connect_descriptor/owa/HelloWorld
- How to do multi-user updates using the Oracle WebServer?
Answer:
Because the Web is stateless, there is no way to lock data between a SELECT and an UPDATE initiated from a Web Browser.One workaround is to let the procedure that display the data for updating also store the data values in hidden fields
.Eg:
for c1 in (select rowid, a.* from emp a) loop
htp.FormHidden('the_rowid', c1.rowid);
htp.Print('Enter new Employee Name:');
htp.FormHidden('old_ename', c1.ename);
htp.FormText('new_ename', c1.ename);
end loop;
The update procedure can now compare the hidden values in the form with the current table values before allowing the update to continue.
Eg:
UPDATE emp SET ename = new_ename
WHERE rowid = the_rowid
AND ename = old_ename;
if (SQL%ROWCOUNT = 0) then
htp.print('Someone else changed this row, please re-query before updating.');
else
htp.print('1 row updated.');
end if;
- Can one use Designer/2000 to generate Web applications?
Answer:
Yes.
From Designer/2000 1.3W one can generate applications that can do Insert, Update and Delete operations.
- Should I access Oracle via the CGI interface or the WRB?
Answer:
The Oracle Web Request Broker (WRB) is faster and more scalable than the CGI-BIN program OWA, but can only be used with certain Web servers.CGI programs are spawned off each time a HTTP request is made to it while the WRB will only start new brokers if the workload increases.
Note that the OWS-BIN OWA program's configuration parameters are stored in the SV*.CFG file while the WRB OWA is configured from SV*.APP.
- Can I store and retrieve images from an Oracle table?
Answer:
Sure you can, consider the following:
- Oracle freely distributes a few unsupported CGI utilities that can do just that.Ask them for their IMGLOAD/ OWAI/ OWAUP utilities.
- If you want to stream multiple IMAGES concurrently from a database table to Web Browsers look at OWA2.
- How does one use HTTP COOKIEs?
Answer:
Cookies allow any site to store information on a WEB Browser's hard disk (cookie.txt file).This information is sent back to the originating site whenever you access it again.
Look at this code example:
owa_util.mime_header ('text/html', FALSE);
owa_cookie.send (cuid, xsession_id, sysdate);
owa_util.http_header_close;
- I've lost the Web Server Administrator's password.What can I do?
Answer:
The Oracle WebServer Administrator's userid and password can be found in your $ORACLE_HOME/ows21/admin/svadmin.cfg file.The password is not encrypted!!!
- Can a Web page be refreshed/reloaded after a given interval?
Answer:
Yes,
- Why do I get "Requested URL was not found on this server"?
Answer:
Symptom:
When attempting to access URLs such as:
http://host:port/ows-bin/service/owa/proc
the server responds with "Requested URL was not found on this server".
Causes:
- This is due to there not being a mapping in the service listener's Virtual Directory Mappings configuration, of the form: /home/oracle/ows2/bin/ CN /ows-bin/service/ so the "owa" program isn't found.
- You're accessing a directory, /xxxx/, and the directory isn't readable by the Web Server process.
- The Web Server is configured to not generate directory listings automatically, and there isn't an index.html file (or whatever you've picked as your index file name).
Fix:
- Create the virtual directory mapping, halt the listener, and restart it.
- Check and fix the directory permissions.Note also the directory rescanning issue below.
- Make sure that either the Web Server will create indices itself, or that there is a readable index file under the name you've specified.If altering the server configuration, halt and restart the server.
- Why do I get "Request failed.We were unable to process your request at this time.Please try again later"?
Answer:
Symptom:
When attempting to access URLs such as:
http://host:port/ows-bin/service/owa/proc
the server responds with "Request failed.We were unable to process your request at this time.Please try again later."
Cause:
- The listener can't read the configuration file owa.cfg.
- The listener is attempting to invoke the PL/SQL procedure named, but can't, for some reason.
Fix:
- Make sure that the file /home/oracle/owa2/admin/owa.cfg is readable by the user running the Web Server.
- Check that the user for the listener has the permissions to invoke such functions: do "exec tw.ping" in sqlplus.There won't be any output, but it should say that it ran ok.If necessary, try reloading the stored procedures into the database.
- Make sure that the names of the input fields in the form match up exactly with the names of the parameters in the script.There must be a one-to-one mapping.
- If you've got multiple-value fields, such as SELECTs, make sure they're of the right type (defined in the OWA_UTIL package), and that there's an extra value supplied by a hidden field to force at least one value to be selected.
- If all else fails, the procedure is probably raising an exception.Put OTHERS exception handlers around everything and call barf(errstr('procedure name')), or the moral equivalent on your system.
