This section contains frequently asked questions about FRIL. If you have questions that are not answered here, please contact us.

1. How do I check my java version?
On Windows machine, open command line (Start->Run, type cmd and hit OK or Run). When the window opens, type 'java -version' (do not type the quotation marks) and hit enter. On mac, open Terminal (Applications->Terminal) and type 'java -version'. Then hit enter. On Linux/UNIX system, open shell and type 'java -version'. Hit enter. What you should see is your current java version. If the number you see starts with 1.6, then you are good to go! If not, go to http://java.sun.com and download java 1.6 for your system.

2. I have java 6 installed, but FRIL does not start.
There might be a few reasons for that. First, you have to make sure that you see correct version number when you check your java version using the same method as presented in answer to the first question. You can have java 6 installed, but your system can be configured in such a way that it uses actually some older java version. Please read the README.txt for more information.

3. I have java 6 and installed FRIL. When I try to start it on my Mac/Linux/UNIX machine, it does not start.
Make sure the file you are using to start FRIL is executable. To do that open Terminal (on Mac machine) or shell (Linux/Unix) and go to the main directory of FRIL; use command 'cd FRIL_DIR' (replace the string FRIL_DIR with path to your FRIL installation). Then change the permissions to the file you use to start FRIL (either fril.sh or fril.sh.command) using the command 'chmod 755 fril.sh' or 'chmod 755 fril.sh.command'.

4. I have two files, one has very large number of records, the second one is quite small. I expect the data from the smaller file to be a subset of data from the larger one. Which file should be used for the upper data source, the larger or the smaller one?
It really does not matter. FRIL will work either way. Usually, for such scenario we use the larger file for the upper data source and the smaller file for the lower one.

5. Why is the option of summary of not joined data disabled for some search methods (e.g., I can only select summary for the first data source for nested loop join)?
This is dictated by the specifics of particular search method. As each method works in different way, we are able to generate summary information for some of them. For other, it would be very hard to implement this feature in an efficient way.

6. My machine has X GBs of RAM. Why FRIL is showing that it has only Y MBs of available memory?
FRIL uses java, and thus its memory is maintained by java virtual machine (JVM). By default, JVM that starts FRIL is configured to use at most 500MBs of RAM. You can change this setting easily. Just edit the file you use to start FRIL and locate the text "-Xmx=...". You should see some number instead of "...". Change this number to desired value. Remember that 1024MB = 1GB.

7. My machine has X GBs of RAM, and I am still getting warning about insufficient memory. How is that possible?
Please read an answer to the previous question. You might want to increase the memory available for java virtual machine.

8. How do I use JDBC database connections? Can I create connection to any database?
FRIL comes with JDBC drivers for MSSQL Server, Oracle, MySQL and PostgreSQL databases. Additionally, a driver that provides connection to MSSQL Server that uses windows login information is provided. If you want to connect to any other database, you have to search for appropriate JDBC driver. Once you download the JDBC driver (it should be a file with extension ".jar"), you need to place it in the jdbc directory located in the main FRIL directory (it is very important to place the driver in that directory - otherwise FRIL will not recognize properly your driver). Now you can configure the connection (database location). Note that you may need to look for appropriate connection format that you need to use with the driver you downloaded. Also note that some connections can be configured with FRIL help (click on button that reads "..." next to the Database location parameter). FRIL will help you with configuration of database connections to such databases as: MSSQL Server, Oracle, MySQL and PostgreSQL. Using FRIL you can also connect to any not mentioned above database provided that its vendor has a JDBC driver you can use. When you are configuring a JDBC connection, you need to specify the JDBC driver class that will be used. If you use FRIL help in the configuration process, the driver will be suggested automatically for MSSQL Server, Oracle, MySQL or Postgres, once you configure the Database location parameter.