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9.3 OracleAS Reports Services

Oracle Reports, like Oracle Forms, is a part of the
Oracle Developer Suite and has been a part of the Oracle technology
stack for many years. We discuss the use of Oracle Reports in the
context of business intelligence solutions in Chapter 12, but an in-depth discussion of the use and
capabilities of Oracle Reports is beyond the scope of this chapter.

In brief, Oracle Reports enables a developer to combine data from
many sources (including an Oracle database, XML data, JDBC data
feeds, and even customizable data sources) into a report that can be
distributed either on paper or within the web environment. Reports
can be generated as HTML, XML, PDF files, RTF format, and many other
formats as well.

This section concentrates on Oracle Application Server Reports
Services, the component of Oracle Application Server that is
responsible for providing a middle tier for deploying Oracle Reports.
OracleAS Reports Services is responsible for creating Oracle Reports
engines to generate reports, for distributing reports across multiple
servers, and for caching reports for rapid reuse.

9.3.1 How It Works

OracleAS Reports Services can be used either
inside or outside a web environment. The architecture of OracleAS
Reports Services within a web environment is shown in simplified form
in Figure 9-2.

Figure 9-2. Simplified OracleAS Reports Services architecture

Requests come into the Oracle HTTP Server, and are then passed to an
OracleAS Reports servlet through the
mod_oc4j module. The

OracleAS Reports servlet is
responsible for coordinating requests with the OracleAS Reports
Server. The server handles the processing, scheduling, and
distribution of reports. It also maintains the state of all current
report requests.

The OracleAS Reports Server is monitored and controlled by the
Oracle Process Management and
Notification Server (described in Chapter 2),
although you can start and stop the OracleAS Reports Server in other
waysfor example, with a command-line prompt or from a URL.

The actual creation of reports is handled by
Reports
engines, which are written in C. There can be many Reports engines
for each OracleAS Reports Server. You can configure the maximum,
minimum, and initial number of engines for a OracleAS Reports Server,
as well as the amount of time a Reports engine can be idle before it
is automatically shut down by OPMN.

Several additional components are included in the OracleAS Reports
Services architecture but aren't displayed in the
simplified version shown in the figure:

OracleAS Reports Cache

Used by the OracleAS Reports Server for caching
reports for subsequent use, based on rules established for the
report.

Custom Tag Handler

A part of the Reports
servlet, used to call Oracle Reports
from JSPs with special tags. You can use these
tags to gain access to data models developed in reports.

OracleAS Single Sign-On

Because OracleAS Single Sign-On is a part of Oracle Application
Server, you can use this security architecture with OracleAS Reports
Services. If you choose to use OracleAS Single Sign-On, the Oracle
Reports servlet interacts with the OracleAS Single Sign-On service to
validate user credentials. If a user doesn't exist
in the Oracle Internet Directory, the Oracle Delegated Administration
Services, which allow a user to maintain his login credentials,
prompts the user for connection information, which is stored in the
Oracle Internet Directory. You can also use OracleAS Reports Services
with its own security authentication, although OracleAS Reports
Services is installed using OracleAS Single Sign-On by default.

Security can be implemented at three levels in OracleAS Reports Serviceson the application that calls a report, on the report and its destination resources, or on the underlying data sources for the report.

Pluggable engines

These are custom engines that can hook into the OracleAS Reports
Server to use its capabilities, such as scheduling, distribution, and
content. OracleAS Reports Services comes with a URL engine, which
lets you distribute content from any publicly available URL using
these features of the OracleAS Reports Server.

Reports CGI

Used to call reports dynamically from a browser using CGI, and
included for backward compatibility.

You can invoke OracleAS Reports Services from outside a web
environment. You can use the command-line argument
rwclient to call the OracleAS Reports Server
directly. You can also call the OracleAS Reports Server from the
SRW built-in PL/SQL package or can expose OracleAS
Reports Services as a Web Service.

9.3.2 Handling Requests

A request that comes into an OracleAS Reports Server can include
parameters that shape the report. If the request is made from a
browser, the parameters can be included in the calling URL, or that
URL can use a key to identify a group of parameters. The parameter
groups and values are stored by key name in the
cgicmd.dat file.

When a request comes in to an OracleAS Reports Server, the server
first determines if the request can be satisfied either by a
currently running job or by a report in the OracleAS Report Cache,
described in the next section. If a request can't be
satisfied by one of these two methods, the request is placed in one
of two queues:

Current job queue

For immediate requests

Scheduled job queue

For scheduled requests

OracleAS Reports Services also has two more queues:

Completed jobs queue

For job history; you can configure a limit to the number of jobs kept
in the completed jobs queue

Failed jobs queue

For failed jobs

OracleAS Reports Server keeps requests that come from a browser in
memory. In the event of a server crash, these requests will have to
be resubmitted. Requests that are slated for a print queue, a file,
or OracleAS Portal will be restarted in the event of an OracleAS
Reports Server failure.

You can view the contents of either the current job queue or the
scheduled job queue through the Application Server Control tool in
Oracle Enterprise Manager. Both of these queues are persistent; if an
OracleAS Reports Server crashes, only the currently running jobs are
lost.

If a request requires authentication, OracleAS Reports Server calls
the mod_osso module before placing the requests in
either queue.

You configure the maximum number of Reports engines for an OracleAS
Reports Server. If a request is made, and the maximum number of
Reports engines aren't currently running, OracleAS
Reports Server creates a new engine to run the request at the top of
the current job queue. If the maximum number of engines are already
running, the top job in the current job queue waits, and the first
available engine takes the job.

Internal testing from Oracle has determined that the optimal number of Reports engines is two times the number of CPUs on a server.

With Oracle Application Server 10g, several
different Reports engines can exist with different environment
conditions, such as the ability to handle reports with different
languages. When a report request arrives with a particular
configuration, OracleAS Reports Server directs it to an available
Reports engine that is appropriate for the request.

Once a Reports engine has completed the creation of the report, the
report is placed in the OracleAS Reports Cache, and the OracleAS
Reports Server is notified of its availability. The OracleAS Reports
Server then distributes the report.

The steps described here are valid for running reports with a paper
layout, whether they are standard reports or JSP reports. If you want
to display a report with a paper layout in a browser, the report can
be sent as an Adobe Acrobat (PDF) file format. If you want to run a
report with a web layout, you can save the report definition as a JSP
in Oracle Forms Developer and then execute the report like a standard
JSP.

9.3.3 OracleAS Reports Cache

A report is a static view of constantly
changing data. There may be times when the same report can fulfill
more than one requesteither by design or by the coincidences
of usage patterns. Consequently, OracleAS Reports Services tries to
optimize the use of reports and diminish the resource requirements
for serving reports to a user community.

As mentioned earlier, the destination for reports created by a
Reports engine is the OracleAS Reports Cache. When a report is put
into that cache, the report is assigned a cache key. The cache key
includes most of the parameters that shape the report, with the
exception of destination information, server information, and the
TOLERANCE parameter (described later in this section). You can
configure an OracleAS Reports Server instance to ignore specified
parameters in creating the cache key.

When a request comes in, the OracleAS Reports Server looks in the
OracleAS Reports Cache for a report with the same cache key. A report
in the cache with an identical cache key can sometimes be reused for
another request.

The request itself can include the TOLERANCE parameter. This
parameter has a value in minutes, hours, or day, or alternately
contains a specific time. If a report has a TOLERANCE parameter, the
OracleAS Reports Server searches the completed jobs queue for a
report with an identical cache key that isn't older
than allowed by the time value specified by the TOLERANCE parameter
or earlier than the time specified by that parameter.

The size of the OracleAS Reports Cache is configurable, either by the
total size of the cache or by the number of documents the cache is
allowed to hold. As the cache is filled, the least-used reports are
swapped out of the cache.

9.3.4 Distributing Reports

Once a report is created, it can be
distributed to a variety of destinationsfor example, to the
browser issuing a request, to one or more recipients via email, to a
file or a printer, or to OracleAS Portal. You can also create your
own custom destinations using the Oracle Application Server
Reports Services API. That API supports
the distribution of reports to other destinations, such as via FTP or
a fax machine.

With Oracle Application Server 10g, the creation
of reports is done by the Reports engine, independent of the eventual
destination of the report. The OracleAS Reports Server is responsible
for distributing the report to its final destinations.

You can create complex types of distributions for reports. Each
report has three distinct sectionsa header, a trailer, and a
body. You can distribute each section separately, and you can also
create individual reports based on groups specified in the body of
the report. You can send each report or report section to one or more
destinations. You can also create destinations based on one or more
data values in a variable.

For example, if you have a report on employees by department, you can
have a department summary section sent to the appropriate head of the
department, as well as individual employee reports, sent to each
employee. The department heads and employees can be indicated by data
variables within the report. This scenario, sometimes referred to as
bursting reports, allows a single report pass to
generate a wide spectrum of reports.

An XML file is used to describe these complex distributions. You
specify the distribution XML file as part of the report request. For
more information on these complex distributions, please refer to the
Oracle Application Server Reports Services documentation.

9.3.5 XML and Reports Services

The distribution file mentioned in the previous section is an
XML
file. XML (described in greater detail in Chapter 10), which can also be used as a format for
reports or to modify reports with customization files.

Although you can build a report completely from scratch using XML,
Oracle recommends following an alternate process whereby you save a
report as XML. You can apply one or more XML customization files to
the saved report; these files are used to modify characteristics in
the report.

For example, you might want to format a particular field using its
XML attributes in a customization file. Once you have perfected the
XML customization file, you can use it to apply the same formatting
to other reports that contain the same field, either by running each
report or by applying the modifications as part of a batch process.

9.3.6 Clustering

You can cluster together any number of
OracleAS Reports Servers. Each member of the cluster is aware of the
other members of the cluster, and all members of the cluster work
together to handle incoming requests.

When a request comes in to one OracleAS Reports Server in a cluster,
either from a client or off the scheduled job queue, the request will
go through the standard set of steps for determining how to handle
the request, but will supplement each step with an examination of
other members of the cluster. For example, the first step when
receiving a request is to see if there is information in the OracleAS
Reports Cache to handle the request. With a cluster, this step is
followed by a determination of whether there is information in the
OracleAS Reports Caches of any other members of the cluster to handle
the request. The same process is followed when looking for currently
running jobs, for an appropriate Reports engine that is available,
and for checking the number of Reports engines running against the
maximum number of engines configured for the OracleAS Reports Server.

Each member of a cluster maintains its own local
OracleAS Reports Cache, so the failure
of any member eliminates the contents of its cache and prevents
access by the other members of the cluster to this information. Such
failure also prevents access by the OracleAS Reports Server and its
engines.

Clusters are formed by appending a cluster name onto the name of the
OracleAS Reports Server. You can submit a request to the cluster,
rather than to a server in the cluster, by specifying the cluster
name as the server.

9.3.7 Calling OracleAS Reports Services

You can access OracleAS Reports
Services directly from a browser or from the command line. But you
may want to generate or schedule reports based on other interactions
and interfaces. OracleAS Reports Services comes with an API that can
make a request to the services based on a database event, such as a
changed value in the database. Two other interfaces also are
frequently used to access reports from OracleAS Reports
Servicesthrough OracleAS Portal and as a web service. We
describe both of these interfaces in subsequent sections.

9.3.7.1 Event-based reporting

In general, reports are the way that information
in a database is disseminated to groups of users. Oracle Application
Server Reports Services brings many helpful capabilities to this
taskfor example, easily readable presentation, multiple
copies, and ease of access. Historically, however, there has been an
inevitable problem with reports and the data they represent. A report
gives an accurate view of dataat the time the report was
generated. This data can change at any point in time after this
generation. OracleAS Reports Services has a way to overcome this
limitation and make reports more timely.

The OracleAS Reports Services API is a
PL/SQL package that can be called
from any other PL/SQL procedure. The package lets you submit a
request to a OracleAS Reports Server and pass up to 255 parameter
values with the request. Submitting a job returns a job
identification, which can check the status of the job or cancel the
job.

9.3.7.2 OracleAS Portal

OracleAS Portal is another component of
Oracle Application Server, discussed in detail in Chapter 13. You can call reports from OracleAS Reports
Services to be displayed within the OracleAS Portal framework, either
within its own portlet or as an item link on another page.

The interaction between OracleAS Portal and OracleAS Reports Services
requires a few additional considerations. If you are calling a report
from the Portal environment:

You can limit access to the report through
security restrictions on the calling
OracleAS Portal page. Because OracleAS Portal uses OracleAS Single
Sign-on, a user identity flows to OracleAS Reports Services, which
imposes its own set of report and data access security restrictions.

You must register all OracleAS Reports Servers and reports in your
OracleAS Portal environment

You can use availability calendars in OracleAS Portal to restrict the
days and times that reports can be requested from OracleAS Reports
Services.

Although you can publish a report to OracleAS Portal, you
can't use OracleAS Portal as a destination when you
are using an XML distribution file.

9.3.7.3 Web Services

Web Services are a way to
access some kind of functionality or information over the Web, using
XML to describe the information requested.

If you want to run OracleAS Reports Services as a Web Service, you
run the rwwebservices OC4J servlet. This
application provides endpoints for accessing an OracleAS Reports
Server as a Web Service. Other applications can use this servlet to
get the version of the API used to access the OracleAS Reports
Server, get information about the server or any particular job, and
submit and kill jobs for the OracleAS Reports Server.