Some prerequisite Before using API.

If we want to call any API using backend then we need to take care for the below mentioned points.

set policy context.
mo_global.set_policy_context(access_mode,org_id)

Calling Program Context before using any API.

fnd_global.apps_initialize ( user_id in number,

                                      resp_id in number,

                                     resp_appl_id in number,

                                     security_group_id in number default 0);

Return Status after using API. (x_return_status)

• Success (FND_API.G_RET_STS_SUCCESS)

• Error (FND_API.G_RET_STS_ERROR)

• Unexpected error (FND_API.G_RET_STS_UNEXP_ERROR)

Messages

FND_MSG_PUB.Initialize  or    p_init_msg_list   Default  FND_API.G_FALSE

Debug Messages after using API.

arp_standard.enable_file_debug(<pathname>, <filename>)

<pathname> 

select value from v$parameter where name = 'utl_file_dir',

arp_standard.enable_file_debug ('/sqlcom/log','txt.log')

To get the resp_id and resp_appl_id use the below queries

SELECT APPLICATION_ID, RESPONSIBILITY_ID

                          FROM FND_RESPONSIBILITY_TL

                          WHERE RESPONSIBILITY_NAME='xxmz Custom';

SELECT USER_ID FROM FND_USER WHERE USER_NAME='OPERATIONS';

API for getting Error messages in program after using API.

pa_interface_utils_pub. get_messages

                                    (p_encoded        IN   VARCHAR2  ,

                                      p_msg_index      IN NUMBER    ,

                                      p_msg_count      IN NUMBER    ,

                                      p_msg_data       IN  VARCHAR2  ,

                                      p_data             OUT NOCOPY           VARCHAR2,  

                                      p_msg_index_out  OUT NOCOPY    NUMBER  

                                     );