Prepare the runtime environment - connecting to the database

In order to connect to PostgreSQL, you must have a PostgreSQL database driver "dbmpgs" in $FGLDIR/dbdrivers.
The PostgreSQL client software is required to connect to a database server.
Check whether the PostgreSQL client library (libpq.*) is installed on the machine where the BDL programs run.
Make sure that the PostgreSQL client environment variables are properly set.
Check, for example, PGDIR (the path to the installation directory), PGDATA (the path to the data files directory), etc. See the PostgreSQL documentation for more details.
Check the database client locale settings.
The database client locale must match the locale used by the runtime system (LC_ALL, LANG).

With PostgreSQL, the default client encoding is the database encoding. If the application locale is different than the database locale, set the database client locale with client_locale in postgresql.conf, or the PGCLIENTENCODING environment variable.

Verify the environment variable defining the search path for the PostgreSQL database client shared libraries (libpq.so on UNIX™, LIBPQ.DLL on Windows™).

Table 1. Shared library environment setting for PostgreSQL
PostgreSQL version	Shared library environment setting
PostgreSQL 11 and higher	UNIX: Add $PGDIR/lib to LD_LIBRARY_PATH (or its equivalent). Windows: Add %PGDIR%\bin to PATH.

To verify if the PostgreSQL client environment is correct, you can start the PostgreSQL command interpreter:
```
$ psql dbname -U appadmin -W
```
Set up the FGLPROFILE entries for database connections.
1. Define the PostgreSQL database driver:
```
dbi.database.dbname.driver = "dbmpgs"
```
2. The 'source' parameter defines the name of the PostgreSQL database, as well as additional connection parameters if needed, such as the server host name, the TCP port and specific PostgresSQL connection options.
```
dbi.database.dbname.source = "test1"
```
  The source parameter must have the following form:
```
dbname[@host[:port]][?options]
```
  where:
  - dbname defines the name of the PostgreSQL database
  - host defines the server host name, or IP address (IPv6 host address needs to be enclosed it in square brackets)
  - port defines the TCP port
  - options is a URI-style query string defining PostgreSQL connection parameters
  For example:
```
mydb@orion:5433?connect_timeout=10&application_name=myapp
```
3. Define pre-fetch rows.
  To improve performances, you can define the number of result set rows that the driver must prefetch:
```
dbi.database.dbname.pgs.prefetch.rows = integer
```
  This will be applied to all application cursors.
  
  The default is 50 rows. Do not change the default, except if it gives really better performances: This can blow up memory usage for each DB client process.
  
  For more details, see PostgreSQL specific FGLPROFILE parameters.
To configure a secure connection to PostgreSQL server using TLS, see Server-side configuration for secure connections with PostgreSQL