FAQs

• How do I remove a file with funny characters in the filename ?

  If the 'funny character' is a '/', skip to the last part of this answer. If the funny character is something else, such as a ' ' or control character or character with the 8th bit set, keep reading. The classic answers are rm -i some*pa...

• How do I remove a file whose name begins with a "-" ?

  Figure out some way to name the file so that it doesn't begin with a dash. The simplest answer is to use rm ./-filename (assuming "-filename" is in the current directory, of course.) This method of avoiding the interpretation of the "-" wo...

• What do I need to know about file permissions and "chmod"?

  Unix systems are designed for multiple users, and include provision for protecting your work from unauthorised access by other users of the system. The file permissions determine who is permitted to do what with your programs, data, and...

• How do I decode the data in my Form?

  The normal format for data in HTTP requests is URLencoded. All Form data is encoded in a string, of the form param1=value1&param2=value2&...paramn=valuen Many non-alphanumeric characters are "escaped" in the encoding: the character w...

• What is the "CGI Overhead", and should I be worried about it?

  The CGI Overhead is a consequence of HTTP being a stateless protocol. This means that a CGI process must be initialised for every "hit" from a browser. In the first instance, this usually means the server forking a new process. This...

• Do I have to use Perl?

  No - you can use any programming language you please. Perl is simply today's most popular choice for CGI applications. Some other widely- used languages are C, C++, TCL, BASIC and - for simple tasks - even shell scripts.

• Do I need to be on Unix?

  No, but it helps. The Web, along with the Internet itself, C, Perl, and almost every other Good Thing in the last 20 years of computing, originated in Unix. At the time of writing, this is still the most mature and best-supported pla...

• Should I use CGI or an API?

  APIs are proprietary programming interfaces supported by particular platforms. By using an API, you lose all portability. If you know your application will only ever run on one platform (OS and HTTPD), and it has a suitable API, go a...

• Should I use CGI or JAVA?

  CGI and JAVA are fundamentally different, and for most applications are NOT interchangable. CGI is a protocol for running programs on a WWW server. Whilst JAVA can also be used for that, and even has a standardised API (the servlet,...

• When do I need to use CGI?

  There are innumerable caveats to this answer, but basically any Webpage containing a form will require a CGI script or program to process the form inputs.

• Is it a script or a program?

  The distinction is semantic. Traditionally, compiled executables (binaries) are called programs, and interpreted programs are usually called scripts. In the context of CGI, the distinction has become even more blurred than before....

• What is CGI?

  The Common Gateway Interface, or CGI, is a standard for external gateway programs to interface with information servers such as HTTP servers. A plain HTML document that the Web daemon retrieves is static, which means it exists in a const...

• What are cubes?

  Cubes are data processing units composed of fact tables and dimensions from the data warehouse. They provide multidimensional views of data, querying and analytical capabilities to clients.

• What are aggregations?

  Aggregations are precalculated numeric data. By calculating and storing the answers to a query before users ask for it, the query processing time can be reduced. This is key in providing fast query performance in OLAP.

• What are measures?

  Measures are numeric data based on columns in a fact table. They are the primary data which end users are interested in. E.g. a sales fact table may contain a profit measure which represents profit on each sale.

• What are fact tables?

  A fact table is a table that contains summarized numerical and historical data (facts) and a multipart index composed of foreign keys from the primary keys of related dimension tables.

• What are dimensions?

  Dimensions are categories by which summarized data can be viewed. E.g. a profit summary in a fact table can be viewed by a Time dimension (profit by month, quarter, year), Region dimension (profit by country, state, city), Product dimension...

• What is OLTP?

  OLTP stands for Online Transaction Processing. OLTP uses normalized tables to quickly record large amounts of transactions while making sure that these updates of data occur in as few places as possible. Consequently OLTP database are desi...

• What is OLAP?

  OLAP stands for Online Analytical Processing. It uses database tables (fact and dimension tables) to enable multidimensional viewing, analysis and querying of large amounts of data. E.g. OLAP technology could provide management with fast a...

• What are the benefits of data warehousing?

  Data warehouses are designed to perform well with aggregate queries running on large amounts of data. The structure of data warehouses is easier for end users to navigate, understand and query against unlike the relational databases prim...

• What is a data mart?

  A data mart is a segment of a data warehouse that can provide data for reporting and analysis on a section, unit, department or operation in the company, e.g. sales, payroll, production. Data marts are sometimes complete individual data war...

• What is a data warehouse?

  A data warehouse is a collection of data marts representing historical data from different operations in the company. This data is stored in a structure optimized for querying and data analysis as a data warehouse. Table design, dimensions...

• Foreword to Extended Pascal standard with history and list of features

  Here is part of the foreword from the Extended Pascal standard to provide some history of it (and of unextended Pascal).

• Required Interfaces to Extended Pascal

  The Extended Pascal standard includes 2 concepts that provide hooks for interfaces to things outside of Pascal.

• Various suggestions for enhancements/changes to the Pascal standards

  If you have comments, suggestions, opinions, etc. about future Pascal standards work, please speak up! Send them to the committee and we'll put them on the agenda. However, to be honest, without a person who has an interest in the new featu...

• Comparison of Borland Pascal to the Pascal standards

  As mentioned earlier, Turbo Pascal does not conform to any of the Pascal standards. If you carefully chose a subset of unextended Pascal, you may be able to port code if you're lucky/careful.

• How to find compilers for each standard?

  For unextended Pascal, there are dozens of compilers that accept unextended Pascal programs. They range from PCs (Prospero Pascal) to large Digital Alpha machines, IBM mainframes, HP workstations, etc.. Unfortunately, Turbo Pascal does not...

• Anymore standards in progress?

  Recently, the committee has been working on an exception handling model that is similar to what you might see in C++ or Modula-3. We hope to produce another ANSI Technical Report on this in the future. However, we're in need of more people...

• Who creates the standards?

  The Pascal standards are development and maintained by the American committee, X3J9, and the International working group, WG2. Most of the standarizers actually belong to both committees.

• What are the different Pascal standards?

  There are currently 3 different documents that can be classified as Pascal standards: Unextended Pascal, Extended Pascal, and the Object-Oriented Extensions to Pascal.

• Why does the message "9031 Unable to initialize link C10LINK2. Reason=AppcReturnCode::UnrecognizedModeName" appear in the WebLogic log or the CRM standard error file?

  The most probable cause is that the mode name specified in the console is not recognized by the back-end system. To correct this: 1. Verify that the mode name is a valid VTAM mode name for your system. 2. For IMS or batch, verif...

• Why does the message "WARN: Inbound Exchange Logs Rejected for <link_name>" appear in the WebLogic log or the CRM standard error file?

  The most probable cause is that there is a discrepancy in the exchange logs. The affected links should be cold started.

• Why does the message "java.net.ConnectException: Connection refused: connect" appear in the WebLogic log?

  The most probable cause is the Gateway was unable to connect to the CRM.

• Why does the error message "JAM CRM Gateway: license has expired on <date>" appear in the WebLogic log?

  WebLogic JAM is delivered with a short-term evaluation license. Contact your Sales Representative for a long-term product license.

• Why does the message "ERROR: CRM client message rejected -- incompatible software/protocol version (CRMAPI RC=<text>)" appear in the WebLogic log or the CRM standard error file?

  The most probable cause is that different versions of the WebLogic JAM Gateway and CRM are being connected. Verify that current versions of both components are in use.

• Why does the message "ERROR: CRM Logical Unit <logical_unit> is probably inactive or unconfigured" appear in the WebLogic log or CRM standard error file?

  The most probable cause is that the CRM logical unit is not active. To correct this: 1. Verify that the CRM logical unit name is correct. 2. Verify that the CRM logical unit has been activated in VTAM.

• I cannot activate a CRM link. Why?

  The most probable cause is incorrect values for the Maximum Session and Minimum Winner Session fields. The total of the Minimum Winner Session values on each peer of the connection must be less than or equal to the Maximum Session value.

• How do I enable Gateway tracing?

  You use the WebLogic Administration Console to set the Gateway tracing levels. For instructions, refer to Modifying Trace Level Settings in the BEA WebLogic Java Adapter for Mainframe Configuration and Administration Guide.

• How do I view Gateway statistics?

  You use the WebLogic Administration Console to view Gateway statistics. For instructions, refer to Monitoring a Gateway in the BEA WebLogic Java Adapter for Mainframe Configuration and Administration Guide.

• How do I start/stop the Gateway?

  You use the WebLogic Administration Console to start and stop a Gateway. For instructions, refer to Starting and Stopping a Gateway in the BEA WebLogic Java Adapter for Mainframe Configuration and Administration Guide.

• What is the difference between group by and order by?

  Group by controls the presentation of the rows, order by controls the presentation of the columns for the results of the SELECT statement.

• What is a subselect? Is it different from a nested select?

  A subselect is a select which works in conjunction with another select. A nested select is a kind of subselect where the inner select passes to the where criteria for the outer select.

• Explain an outer join.

  An outer join includes rows from tables when there are no matching values in the tables.

• What is a view? Why use it?

  A view is a virtual table made up of data from base tables and other views, but not stored separately.

• What techniques are used to retrieve data from more than one table in a single SQL statement?

  Joins, unions and nested selects are used to retrieve data.

• Explain the use of the WHERE clause.

  WHERE is used with a relational statement to isolate the object element or row.

• Describe the elements of the SELECT query syntax.

  SELECT element FROM table WHERE conditional statement.

• What are foreign keys?

  These are attributes of one table that have matching values in a primary key in another table, allowing for relationships between tables.

• What is normalization and what are the five normal forms?

  Normalization is a design procedure for representing data in tabular format. The five normal forms are progressive rules to represent the data with minimal redundancy.

• What is the basic difference between a join and a union?

  A join selects columns from 2 or more tables. A union selects rows.