To create a Catalina client, write the appropriate Python script:

This one prints name, account and QOS for every job:
----------------------------------------------------------------
#!/usr/local/apps/python/bin/python
import sys
sys.path.append('/paci/loadl/catalina/install')
import Catalina

# Open database for read access:
jobs_db_handle = Catalina.open_ro_db(Catalina.JOBS_DB, 'read')

# Retrieve a dictionary of jobs:
jobs_dict = jobs_db_handle[0]

# For every job, print its name, account and QOS:
for job in jobs_dict.values() :
    print "name: %s, account: %s, QOS: %s" % \
      (job['name'], job['account'], job['QOS'])

# Close the database:
Catalina.close_ro_db(jobs_db_handle)
----------------------------------------------------------------

This one opens the database in write mode, to allow changing a reservation.
This example takes a res id and a comma-delimited list of users
and sets the job_restriction for that reservation to allow a job
by any of the specified users.
----------------------------------------------------------------
#!/usr/local/apps/python/bin/python

# Import the sys module
import sys

# Add the path to the Catalina module
sys.path.append('/paci/loadl/catalina/install')

# Import the Catalina module
import Catalina

# Import some useful utility modules
import getopt
import re

# set the list of accepted command line options
options = ['res_id=', 'users=']

# Retrieve command line args
args = sys.argv[1:]

# Parse the long options
optlist, lineargs = getopt.getopt(args, '', options)
argdict = {}
for pair in optlist :
    argdict[pair[0]] = pair[1]

# Exit, unless both --res_id and --users were provided
if not argdict.has_key('--res_id') or not argdict.has_key('--users') :
    print "both --res_id=<reservation id> and --users=<users list> required!"
    sys.exit(1)

# Change the users string into a string that forms a Python list of users
# "['user1','user2','user3',...]"
users_string = argdict['--users']
if users_string != '' :
    users_string = "['" + users_string + "']"
    users_string = re.sub(",", "','", users_string)
else :
    users_string = '[]'

# Set res_id
res_id = argdict['--res_id']

# Form the Python job restriction code fragment restricting the reservation
# to jobs with a user in the list
job_restriction = \
  "if input_tuple[0]['user'] in " + users_string + " : result = 0"

# Get the reservations database name from the Catalina module
RESERVATIONS_DB = Catalina.RESERVATIONS_DB

# Open the reservations database in 'write' mode, get the handle
reservations_db_handle = Catalina.open_db(RESERVATIONS_DB,'write')

# With exception handling, retrieve the specified job
try :
    temp_res = Catalina.get_object(res_id, reservations_db_handle)
except 'KeyNotFound' :
    print "Reservation (%s) not found in Catalina DB" % res_id
    Catalina.close_db(reservations_db_handle)
    sys.exit(1)

# Use the Catalina update_object_attribute method to change an object
Catalina.update_object_attribute(
  'job_restriction', job_restriction, temp_res, reservations_db_handle
  )

# Close the database.  Changes don't take effect until the DB is closed
Catalina.close_db(reservations_db_handle)
----------------------------------------------------------------


Databases are listed in catalina.quickstart.  The three main ones are:
RESERVATIONS_DB
RESOURCE_DB
JOBS_DB

Catalina methods for manipulating databases and objects:

open_db(db_name, db_mode)
    This opens the specified db, pausing the scheduler iteration.
    db_name should be the string representing the database.
    db_mode can be 'write' or 'read'.
    The database handle is returned

close_db (db_handle)
    closes the database

open_ro_db (db_name, db_mode)
    This opens the readonly cache file for the db.  The scheduler is not
    paused.

close_ro_db (db_handle)
    closes the database

update_object_attribute(name, value, object, db_handle)
    after an object is retrieved from the database, it can be modified
    with this method.
    name is the name of the attribute to change
    value is the value to assign to the attribute
    object is the object to be modified
    db_handle is the database containing the object

delete_object(name, db_handle)
    deletes object from database
    name is name of the object
    db_handle is the database containing the object