def _applicationStart(self, data):
checkup = False<EOL>if "<STR_LIT>" in self.application.configand isinstance(self.application.config["<STR_LIT>"], dict):<EOL><INDENT>if "<STR_LIT:host>" in self.application.config["<STR_LIT>"] and"<STR_LIT:port>" in self.application.config["<STR_LIT>"] and"<STR_LIT:name>" in self.application.config["<STR_LIT>"]:<EOL><INDENT>if len(self.application.config["<STR_LIT>"]["<STR_LIT:host>"]) > <NUM_LIT:0> andself.application.config["<STR_LIT>"]["<STR_LIT:port>"] > <NUM_LIT:0> andlen(self.application.config["<STR_LIT>"]["<STR_LIT:name>"]) > <NUM_LIT:0>:<EOL><INDENT>checkup = True<EOL><DEDENT><DEDENT><DEDENT>if checkup is not True:<EOL><INDENT>return<EOL><DEDENT>try:<EOL><INDENT>self._connectionPool = adbapi.ConnectionPool(<EOL>"<STR_LIT>",<EOL>host=self.application.config["<STR_LIT>"]["<STR_LIT:host>"],<EOL>port=int(self.application.config["<STR_LIT>"]["<STR_LIT:port>"]),<EOL>user=self.application.config["<STR_LIT>"]["<STR_LIT:username>"],<EOL>passwd=self.application.config["<STR_LIT>"]["<STR_LIT:password>"],<EOL>db=self.application.config["<STR_LIT>"]["<STR_LIT:name>"],<EOL>charset=self.application.config["<STR_LIT>"]["<STR_LIT>"],<EOL>cp_min=int(<EOL>self.application.config["<STR_LIT>"]["<STR_LIT>"]<EOL>),<EOL>cp_max=int(<EOL>self.application.config["<STR_LIT>"]["<STR_LIT>"]<EOL>),<EOL>cp_reconnect=True<EOL>)<EOL><DEDENT>except Exception as e:<EOL><INDENT>self.log.error(<EOL>"<STR_LIT>",<EOL>error=str(e)<EOL>)<EOL><DEDENT>if "<STR_LIT>" in self.application.config["<STR_LIT>"]and self.application.config["<STR_LIT>"]["<STR_LIT>"]["<STR_LIT>"]:<EOL><INDENT>self._checkIfDatabaseIsEmpty(<EOL>lambda isEmpty:<EOL>self._scheduleDatabaseInit(isEmpty)<EOL>,<EOL>lambda error:<EOL>self.log.error("<STR_LIT>", error=error)<EOL>)<EOL><DEDENT>
Initializes the database connection pool.

:param data: <object> event data object
:return: <void>