A Frequently Asked Questions

• What is mod_plsql?
• What is the PL/SQL Web Toolkit?
• How do I find the version of mod_plsql?
• How do I find the version of the OWA packages?
• How do I install the OWA packages?
• How do I uninstall the OWA packages?
• How do I detect and clean up duplicate OWA packages installed in the database?
• I am getting HTTP error codes while accessing PL/SQL procedures through mod_plsql.
• All my PL/SQL procedures return a "Document contains no data" error in Netscape, or a blank page in Internet Explorer.
• I have a performant PL/SQL procedure, but some of my HTTP requests through mod_plsql take more than 15 seconds.
• Can I use mod_plsql to run applications on my own database?
• How do I create a DAD for mod_plsql?
• What authentication modes are available in mod_plsql?
• What is the mod_plsql Cleanup Thread?
• What kind of database connection pooling is present in mod_plsql?
• How does mod_plsql clean up database sessions?
• What happens when pooled database connections exist in mod_plsql and the database is restarted?
• How does mod_plsql clean up cached content in the file system?
• Can I invoke mod_plsql without a "/pls" prefix in the URL?
• How can I improve PL/SQL and mod_plsql performance?
• What kinds of logging facilities are available in mod_plsql?
• What considerations should I have in mod_plsql for High Availability?
• What considerations should I have in mod_plsql when the database is separated by a firewall?
• How do I assert a different hostname, port, or request_protocol to the PL/SQL application?
• How do I disable access to procedure names that have a specific pattern?
• I see the error "HTTP-503 ORA-12154" in the file ORACLE_HOME/Apache/Apache/conf/error_log. What does this mean?

What is mod_plsql?

mod_plsql is an Oracle HTTP Server plug-in that communicates with the database by mapping browser requests into database stored procedure calls over a SQL*Net connection. It is generally indicated by a /pls virtual path. The mod_plsql gateway provides support for building and deploying PL/SQL-based applications on the Web. PL/SQL stored procedures can retrieve data from database tables and generate HTTP responses containing formatted data and HTML code to display in a Web browser. See the Oracle Database Application Developer's Guide - Fundamentals for more information.

What is the PL/SQL Web Toolkit?

The PL/SQL Web Toolkit enables you to develop Web applications as PL/SQL procedures stored in an Oracle database server. Packages in the toolkit define procedures, functions, and data types that you can use in your stored procedures. See the Oracle Database Application Developer's Guide - Fundamentals for more information.

How do I find the version of mod_plsql?

You can determine the version of mod_plsql by executing the oversioncheck script on the mod_plsql binary.

On UNIX platforms, issue the following command:

ORACLE_HOME/Apache/Apache/bin/oversioncheck ORACLE_HOME/Apache/modplsql/bin/modplsql.so

On Windows platforms, issue the following command:

ORACLE_HOME\Apache\Apache\bin\oversioncheck ORACLE_HOME\bin\modplsql.dll

How do I find the version of the OWA packages?

1. Use SQL*Plus and connect as any user to the database.
2. Execute the following command:

   select owa_util.get_version from dual;
   
   

   This should show the version of the OWA packages. For example, 9.0.4.0.1.

If this query fails, you are having a very old version of OWA packages that does not have versioning. It is recommended that you upgrade to a newer version.

How do I install the OWA packages?

See Section 2.2, "Installing Required Packages" for more information.

How do I uninstall the OWA packages?

OWA packages can be uninstalled by performing the following tasks:

1. Navigate to the directory from where the OWA packages were installed. For example:

   cd ORACLE_HOME/Apache/modplsql
   
   

2. Use SQL*Plus to connect as the owner the OWA packages. This user should be the SYS user, unless you have an old version of the OWA packages.
3. Invoke the script owadins.sql to uninstall the OWA packages.

How do I detect and clean up duplicate OWA packages installed in the database?

The following SQL query can be used to determine the location of the OWA packages:

SELECT OWNER, OBJECT_TYPE
FROM   DBA_OBJECTS
WHERE  OBJECT_NAME = 'OWA'

You will see the following results:

SQL> 

1  SELECT OWNER, OBJECT_TYPE 
2  FROM DBA_OBJECTS 
3* WHERE OBJECT_NAME = 'OWA' 

OWNER  OBJECT_TYPE 
-----  ----------- 
SYS    PACKAGE 
SYS    PACKAGE BODY 
PUBLIC SYNONYM 

If you see more lines than shown in the preceding SQL query, it means that older OWA packages exist in other schemas, which may cause issues for mod_plsql users. In such situations, uninstall all versions of the OWA packages from the database, and reinstall the OWA packages that ship with the product.

I am getting HTTP error codes while accessing PL/SQL procedures through mod_plsql.

mod_plsql logs detailed error messages to the OHS file ORACLE_HOME/Apache/Apache/logs/error_log. Scan this file to understand the problem. For more information on mod_plsql logging, see "What kinds of logging facilities are available in mod_plsql?".

All my PL/SQL procedures return a "Document contains no data" error in Netscape, or a blank page in Internet Explorer.

This problem could occur if you have duplicate OWA Packages installed in the database. See "How do I detect and clean up duplicate OWA packages installed in the database?" for more information.

I have a performant PL/SQL procedure, but some of my HTTP requests through mod_plsql take more than 15 seconds.

The most common reason for this problem is that the middle-tier character set does not match that of the back-end database, and HTTP KeepAlive is enabled in Oracle HTTP Server. This kind of misconfiguration causes an invalid Content-Length to be sent back to the browser, causing the browser to detect the end of the response stream only when the KeepAliveTimeout interval causes the stream to be closed. To solve the problem, ensure that the PlsqlNLSLanguage parameter in the DAD matches that of the database.

Can I use mod_plsql to run applications on my own database?

Yes. But before you can run your applications, you need to install the OWA packages into your database. See Section 2.2, "Installing Required Packages".

How do I create a DAD for mod_plsql?

Refer to the mod_plsql section in the Oracle HTTP Server Administrator's Guide.

What authentication modes are available in mod_plsql?

See Chapter 3, "Securing Application Database Access Through mod_plsql".

What is the mod_plsql Cleanup Thread?

mod_plsql starts a thread in each httpd process. The job of this thread is to clean up idle database sessions and the file system cache. This thread is called the Cleanup Thread.

What kind of database connection pooling is present in mod_plsql?

Refer to Chapter 4, "Optimizing PL/SQL Performance".

How does mod_plsql clean up database sessions?

mod_plsql cleans up unused database sessions based on the configuration setting of PlsqlIdleSessionCleanupInterval. Besides this, the configuration directive PlsqlMaxRequestsPerSession governs how many requests will be serviced from a pooled database session. Finally, database sessions are closed when httpd processes are shut down.

What happens when pooled database connections exist in mod_plsql and the database is restarted?

When the database connection is severed, the first request that attempts to execute a PL/SQL procedure using the severed connection will fail. Subsequent requests will reestablish a database session and start functioning normally. The number of failures will be directly proportional to the number of pooled database sessions. Future versions of mod_plsql will detect dead connections automatically.

How does mod_plsql clean up cached content in the file system?

The cleanup thread scans the file system cache based on the configuration of PlsqlCacheCleanupTime. The default cleanup time is everyday at 11 P.M. local time.

Can I invoke mod_plsql without a "/pls" prefix in the URL?

Yes. Since mod_plsql uses the OHS' Location directive, you can configure any virtual path to be serviced by mod_plsql.

How can I improve PL/SQL and mod_plsql performance?

Refer to Chapter 4, "Optimizing PL/SQL Performance".

What kinds of logging facilities are available in mod_plsql?

• By default, mod_plsql logs alerts/warnings/errors to the OHS error_log file ORACLE_HOME/Apache/Apache/logs/error_log. The amount of information logged by mod_plsql is controlled by the setting of OHS' LogLevel parameter in httpd.conf. By default, this is configured to warn.
• You can also enable performance logging for mod_plsql on a per-request basis as follows:
  1. Edit ORACLE_HOME/Apache/Apache/conf/httpd.conf and set LogLevel to info (default is warn).
  2. Restart OHS using the following command:

     ORACLE_HOME/opmn/bin/opmnctl restartproc type=ohs
     
     

  3. Issue some URLs to mod_plsql and verify that the file ORACLE_HOME/Apache/Apache/logs/error_log starts showing entries as follows:

     [Tue Apr 01 14:54:49 2003] [info] mod_plsql: [perf] 130.35.92.145 
     /pls/app/htp.p status=200 user=scott reqTime=21ms connSU=(null),0ms 
     connRO=(null),0ms connNSSO=HIT,1ms procTime=17ms sessionTidyTime=0ms 
     cache=(null) cookie=(null),0ms pageCalls=0,0ms bytes=5 describe=No,0ms 
     streamTime=0ms pid=175 sessFile=(null) userFile=834\0855 
     sysFile=470\5949 cacheLevel=(null) cacheTime=0ms dbProcTime=15ms 
     id=1049237685:130.35.92.145:373:1 spid=(null) qs=(null) 
     requestTrace=(null) cookieLen=0 cookieValue=(null) reqUserTime=16ms 
     assertUser=(null) subid=(null) authLevel=(null) oraError=0
     
     

• Finally, you can enable debug logging in mod_plsql. This is the highest level of logging and is not recommended for active sites.

  Caution: This mode of logging should be enabled only at the request of Oracle Support.

  In this mode, debug messages are logged to Oracle HTTP Server's error_log file and additional mod_plsql specific logs are created under ORACLE_HOME/Apache/modplsql/logs. Log location is configurable using the PlsqlLogDirectory directive in ORACLE_HOME/Apache/modplsql/conf/plsql.conf. To enable debug level logging:

  1. Edit ORACLE_HOME/Apache/modplsql/conf/plsql.conf and set PlsqlLogEnable to On (default is Off).
  2. Restart OHS using the following command:

     ORACLE_HOME/opmn/bin/opmnctl restartproc type=ohs
     

What considerations should I have in mod_plsql for High Availability?

For high availability, mod_plsql based applications should be aware of the following things:

• The mod_plsql configuration parameter PlsqlDatabaseConnectString should use a connect string format of NetServiceNameFormat so that name resolution happens through an LDAP lookup of Oracle Internet Directory. This enables you to configure the database host:port:service_name information in a central repository, which makes it easier to add or remove RAC nodes when required.
• mod_plsql does not automatically detect dead database connections. In case a back end database goes down, the initial few requests fail. See "What happens when pooled database connections exist in mod_plsql and the database is restarted?" for more information.

What considerations should I have in mod_plsql when the database is separated by a firewall?

If a firewall exists between the middle-tier running mod_plsql, and the back end database, the idle session cleanup interval in mod_plsql should be configured lower than the idle session cleanup interval of the firewall. This ensures that the firewall never closes a connection established by mod_plsql.

How do I assert a different hostname, port, or request_protocol to the PL/SQL application?

• In situations where your OHS instance is front-ended by Web Cache or a Load Balancing Router, there is a need to assert the hostname and port for the site to be that of the Web Cache or the LBR. In such situations, it is recommended that you use the OHS configuration directives ServerName and Port to do the assertion. If for some reason, you do not wish to assert the hostname and port at the OHS level, you can use the mod_plsql configuration directive PlsqlCGIEnvironmentList to assert a different hostname and port to only the PL/SQL applications running under mod_plsql. For example:
  • PlsqlCGIEnvironmentList SERVER_NAME=lbr.us.oracle.com

    Consider using OHS' ServerName directive in httpd.conf instead.

  • PlsqlCGIEnvironmentList SERVER_PORT=9999

    Consider using OHS' Port directive in httpd.conf instead.

  • PlsqlCGIEnvironmentList HTTP_HOST=myservername.us.oracle.com:9999

    Combination of SERVER_NAME:SERVER_PORT.

• Similarly, in cases where your site is accessed externally as an SSL, but is internally running in non-SSL mode (with an SSL accelerator in between), you might want to assert the REQUEST_PROTOCOL as HTTPS so that the PL/SQL application generates SSL links instead of non-SSL links. For example:

  PlsqlCGIEnvironmentList  REQUEST_PROTOCOL=https
  
  

How do I disable access to procedure names that have a specific pattern?

Please refer to the description of PlsqlExclusionList in Section 3.3.1, "Using the PlsqlExclusionList Directive in mod_plsql".

I see the error "HTTP-503 ORA-12154" in the file ORACLE_HOME/Apache/Apache/conf/error_log. What does this mean?

This error means that mod_plsql is unable to connect to the database.

Ensure that:

1. The database is up and running.
2. The username and password information in the DAD is correct.
3. The middle-tier is able to connect to the database using the PlsqlDatabaseConnectString parameter in the DAD.

In most situations, the problem occurs because SQL*Net is not able to resolve the connect string parameter using the configuration information under ORACLE_HOME/network.101/admin.

• For entries configured with TNSFormat or NetServiceNameFormat, validate the connect string information by using tnsping dad_connect_string. For example:

  tnsping "cn=iasdb,cn=oraclecontext"
  

  or

  tnsping iasdb.us.oracle.com
  
  

• For entries configured with SIDFormat and ServiceNameFormat, ensure that the hostname, port, and SID/service_name information match for the database listener. After verifying this, confirm that SQL*Plus can connect to the database using the DAD username, password, and connect string.

If this does not work, refer to the Oracle SQL*Net documentation on how to troubleshoot this further.