Oracle APIs and Version Numbers and API Error Handling

API Error Handling:

Every API has 3 out parameters as x_return_status, x_msg_count and x_msg_data. 
Using these 3 parameters, one can use below code to log or debug error in API's
dbms_output.put_line (SubStr('x_return_status = '||x_return_status, 1, 255));
dbms_output.put_line ('x_msg_count = '||TO_CHAR(x_msg_count));
dbms_output.put_line (SubStr('x_msg_data = '||x_msg_data, 1, 255));
IF x_msg_count >1 THEN
FOR I IN 1..x_msg_count
LOOP
dbms_output.put_line(I ||'.'|| SubStr(FND_MSG_PUB.Get(p_encoded =>FND_API.G_FALSE ), 1, 255));
END LOOP;
END IF;
END;

Explain The API In R12
You can run the following script and get all the packages related to API in Oracle applications, from which you can select APIs that pertain to AP:
SQL> select substr(a.OWNER,1,20) 
, substr(a.NAME,1,30) 
, substr(a.TYPE,1,20)  
, substr(u.status,1,10) Stat 
, u.last_ddl_time 
, substr(text,1,80) Description  
from dba_source a, dba_objects u  
WHERE 2=2  
and u.object_name = a.name  
and a.text like '%Header%'  
and a.type = u.object_type  
and a.name like 'AP_%API%'  
order by  
a.owner, a.name; 

Overview - API In R12
1) The Application Programming Interface or API is a PL/SQL packaged procedure which can be used as an alternative entry point into the system to the traditional online forms
2) The advantage being that the same logic used by the seeded online forms can also be used by other interfaces into the system, thus ensuring that the integrity of the data remains intact
Calling API
1) Ensure it is appropriate to allow that particular business operation
2) Validate the data passed to the API
3) Each API has a number of parameters, most of them mapped with DB column. Every parameter name starts with p_. If the parameter maps onto a database column, the remaining part of the name is usually the same as the column name
4) When calling the APIs, it is strongly recommended that you use Named Notation, instead of Positional Notation

Private APIs

Private APIs are for internal, development use only. Details are not provided to anyone outside of the immediate development environment, nor are they intended for use by anyone outside of the e-Business Suite development environment.

Public APIs

Public APIs are designed for customers and Oracle consultants to integrate non-Oracle systems into Oracle e-Business Suite or to extend the functionality of the base products. Oracle does not support public APIs unless they are published in a reference manual such as this one. The user accepts all risk and responsibility for working with non-published public APIs.

Public, published APIs

Public Published APIs are guaranteed by Oracle to remain valid from release to release and that patches will not alter the API behavior. Public, published APIs are supported by Oracle to the same extent as released software.

For non-published APIs, Oracle expressly does not provide any guarantees regarding consistency of naming, usage, or behavior of any API (public or private) between releases. It is also possible that a patch could alter any characteristic of any non-published e-Business Suite API. As such, those who choose to use these APIs do so at their own risk. However, Oracle does attempt to minimize all changes to public APIs, even if not published.

Note: In Applications release 11.5.9, many of the Applications' PL/SQL server side APIs have been enhanced to utilize the pass by reference semantics of PL/SQL. This improves performance considerably and reduces memory consumption. In the normal processing case (i.e. success), there is no change of behavior, and callers of these APIs are not impacted. However, in the case of exceptions, there is a behavior change which results in assignments being exposed to the caller, which are made in the API prior to any exceptions being raised. The previous behavior would rollback these assignments made by the API if an exception occurred in this API. Developers writing custom extensions to Oracle Applications, or third party integrators which use the standard Applications' APIs should be aware of this change in semantics.

Each published API provides an API specification, and definitions as for its parameters, data structures, and status messages. Sample scripts and documented process flow diagrams are included where applicable.

Note: The words procedure and API are used interchangeably in this document.

API Version Numbers

Oracle APIs incorporate a mechanism called API version numbers. This mechanism:

• Allows an API to differentiate between changes that require you to change your API calling code and those that don't.
• Allows an API to detect incompatible calls.
• Allows you to quickly determine if calling a new version of an API requires you to change any of your code.
• Allows you to easily figure out which version of an API you need to call to take advantage of new features.

Format of API Version Numbers

API version numbers consist of two segments separated by a decimal point. The first segment is the major version number; the second segment is the minor version number. The starting version number for an API is always 1.0.

The following table shows an example of an API Version number and the major and minor version derived from the API version.

API Version Number	Major Version	Minor Version
1.0	1	0
2.4	2	4

If the major version number has changed, then you probably need to modify your programs that call that API. Major version changes include changes to the list of required parameters or changing the value of an API OUT parameter.

If only the minor version number has changed, then you probably do not need to modify your programs.

Current API Version Number for This Package

The API version number for the APIs included in the current version of the CZ_modelOperations_pub package is:

1.0

The local constant that stores this version number is:

l_api_version   CONSTANT NUMBER

Checking for Incompatible API Calls

To detect incompatible calls, programs calling an API must pass an API version number as one of the input parameters. The API can then compare the passed version number to its current version number, and detect any incompatible calls.

The Oracle standard parameter used by all procedures in this package to pass in the API version number is:

p_api_version IN NUMBER

This parameter is required, and has no initial values, thus forcing your program to pass this parameter when calling an API.

If your call to the API results in a version incompatibility, then an error message is inserted in the table CZ_DB_LOGS.

Parameter Specifications

The specifications for the public APIs provided by the Resource Manager define four categories of parameters:

• Standard IN
• Standard OUT
• Procedure specific IN
• Procedure specific OUT

Standard IN and OUT parameters are specified by the Oracle Applications business object API Coding Standards, and are discussed in the following sections.

Procedure specific IN and OUT parameter are related to the API being specified, and are discussed with that individual API.

Standard IN Parameters
1) p_api_version IN NUMBER  
This must match the version number of the API. An unexpected error is returned if the calling program version number is incompatible with the current API version number
2) p_init_msg_list IN VARCHAR2 
The valid values for this parameter are: 
• True = FND_API.G_TRUE 
• False = FND_API.G_FALSE 
• Default = FND_API.G_FALSE 
If set to true, then the API makes a call to fnd_msg_pub.initialize to initialize the message stack. To set to true, use the value, "T". If set to false then the calling program must initialize the message stack. This action is required to be performed only once, even in the case where more 
than one API is called. To set to false, use the value, "F".
3) p_commit IN VARCHAR2  
The valid values for this parameter are: 
• True = FND_API.G_TRUE 
• False = FND_API.G_FALSE 
• Default = FND_API.G_FALSE 
If set to true, then the API commits before returning to the calling program. To set to true, use the value, "T". If set to false, then it is the calling program’s responsibility to commit the transaction. To set to false, use the value, "F".

The following table describes standard IN parameters, which are common to all public APIs provided by Resource Manager.

Standard IN Parameters
Parameter	Data Type	Required	Description
p_api_version	NUMBER	Yes	This must match the version number of the API. An unexpected error is returned if the calling program version number is incompatible with the current API version number (provided in the documentation).
p_init_msg_list	VARCHAR2	Yes	The valid values for this parameter are: True = FND_API.G_TRUE False = FND_API.G_FALSE Default = FND_API.G_FALSE If set to true, then the API makes a call to fnd_msg_pub.initialize to initialize the message stack. To set to true, use the value, "T". If set to false then the calling program must initialize the message stack. This action is required to be performed only once, even in the case where more than one API is called. To set to false, use the value, "F".
p_commit	VARCHAR2(1)	No	The valid values for this parameter are: True = FND_API.G_TRUE False = FND_API.G_FALSE Default = FND_API.G_FALSE If set to true, then the API commits before returning to the calling program. To set to true, use the value, "T". If set to false, then it is the calling program's responsibility to commit the transaction. To set to false, use the value, "F".

Standard OUT Parameters
1) x_return_status OUT NOCOPY VARCHAR2 
Indicates the return status of the API. The values returned are one of the following: 
• FND_API.G_RET_STS_SUCCESS 
Success: Indicates the API call was successful 
• FND_API.G_RET_STS_ERROR 
Expected Error: There is a validation error, or missing data error. 
• FND_API.G_RET_STS_UNEXP_ERROR 
Unexpected Error: The calling program can not correct the error.
2) x_msg_count OUT NOCOPY NUMBER 
Holds the number of messages in the message list.
3) x_msg_data OUT NOCOPY VARCHAR2 
Holds the encoded message if x_msg_count is equal to one 

The following table describes standard OUT parameters, which are common to all public APIs provided by Resource Manager.

Note: All standard OUT parameters are required.

Standard OUT Parameters
Parameter	Data Type	Description
x_return_status	VARCHAR2(1)	Indicates the return status of the API. The values returned are one of the following: FND_API.G_RET_STS_SUCCESS Success: Indicates the API call was successful FND_API.G_RET_STS_ERROR Expected Error: There is a validation error, or missing data error. FND_API.G_RET_STS_UNEXP_ERROR Unexpected Error: The calling program can not correct the error.
x_msg_count	NUMBER	Holds the number of messages in the message list.
x_msg_data	VARCHAR2(2000)	Holds the encoded message if x_msg_count is equal to one.

Parameter Size

Verify the size of the column from the base table for that column when passing a parameter of a specific length. For example, if you pass a NUMBER value, first query to find the exact value to pass. An incorrect value can cause the API call to fail.

Missing Parameter Attributes

The following table describes optional IN parameters which are initialized to pre-defined values representing missing constants. These constants are defined for the common PL/SQL data types and should be used in the initialization of the API formal parameters.

Initialized IN Parameters
Parameter	Type	Initialized Value
g_miss_num	CONSTANT	NUMBER:= 9.99E125
g_miss_char	CONSTANT	VARCHAR2(1):= chr(0)
g_miss_date	CONSTANT	DATE:= TO_DATE('1','j');

These constants are defined in the package FND_API in the file fndpapis.pls. All columns in a record definition are set to the G_MISS_X constant as defined for the data type.

Parameter Validations

The following types of parameters are always validated during the API call:

• Standard IN
• Standard OUT
• Mandatory procedure specific IN
• Procedure specific OUT

Invalid Parameters

If the API encounters any invalid parameters during the API call, then one of the following actions will occur:

• An exception is raised.
• An error message identifying the invalid parameter is generated.
• All API actions are cancelled.

Version Information

It is mandatory that every API call pass a version number for that API as its first parameter (p_api_version).

This version number must match the internal version number of that API. An unexpected error is returned if the calling program version number is incompatible with the current API version number.

Warning: The currently supported version at this time is 1.0. Use only this for the API version number.

In addition, the object version number must be input for all update and delete APIs.

• If the object_version_number passed by the API matches that of the object in the database, then the update is completed.
• If the object_version_number passed by the API does not match that of the object in the database, then an error condition is generated.

Status Messages

Every API must return one of the following states as parameter x_return_status after the API is called:

• S (Success)
• E (Error)
• U (Unexpected error)

Note: It is not required that all status notifications provide a number identifier along with the message, although, in many cases, it is provided.

Each state can be associated with a status message. The following table describes each state.

Status Message and Description
Status	Description
S	Indicates that the API performed all the operations requested by its caller. A success return status may or may not be accompanied by messages in the API message list. Currently, the Resource Manager APIs do not provide a message for a return status of success.
E	Indicates that the API failed to perform one or more of the operations requested by its caller. An error return status is accompanied by one or more messages describing the error.
U	Indicates that the API encountered an error condition it did not expect, or could not handle, and that it is unable to continue with its regular processing. For example, certain programming errors such as attempting to divide by zero causes this error. These types of errors usually cannot be corrected by the user and requires a system administrator or application developer to correct.

Warning and Information Messages

In addition to these three types of possible status messages, you can also code the following additional message types:

• Warnings
• Information

To create a warning message, perform the following steps:

1. Create a global variable to be used to signal a warning condition. For example, this could be similar to the following:

G_RET_STS_WARNING := 'W'

This global variable is not part of the FND_API package.

2. Return this value if the warning condition is encountered. For example, using the same example as in step one, set up the following code in the API to process the warning condition:

x_return_status := G_RET_STS_WARNING

This code replaces the more usual:

x_return_status := fnd_api.g_ret_sts_unexp_error for "U"

3. If desired, perform a similar procedure to create Information messages.

How to get log messages by using fnd_msg_pub.initialize API:

FND_MSG_PUB for error logging in Oracle Applications.

Use the following snipped of code while calling any seeded API in Oracle Applications, like CRM, or Financials.

Put this block exactly under the section where you invoke the private or public API. The errors raised in the API are logged in the following API. Use this code while error logging or while debugging. Comment out the code before moving into production.

IF ( FND_MSG_PUB.Count_Msg > 0) THEN
FOR i IN 1..FND_MSG_PUB.Count_Msg    LOOP
FND_MSG_PUB.Get(p_msg_index     => i,
          p_encoded       => 'F',
          p_data          => out_message,
          p_msg_index_OUT => l_msg_index_OUT );
dbms_output.put_line('l_msg_data :' ||out_message);
END LOOP;
END IF;

FND_GLOBAL.APPS_INITIALIZE for initializing session in Oracle Applications:

FND_GLOBAL.APPS_INITIALIZE is used for initializing the session before calling any public or private API's in Oracle Ebusiness suite. Its not required for all the API's but its recommended that you set this profile before making any calls to either private or public API.

Listed below is a sample call to FND_GLOBAL.APPS_INITIALIZE function

fnd_global.APPS_INITIALIZE(user_id=>l_user_id,
                                                   resp_id=>l_resp_id,
                                                resp_appl_id=>l_resp_appl_id);

1. l_user_id is the fnd user ID which will be utilized during the call.
2. l_resp_id is the responsibility ID
3. l_resp_appl_id is the responsibility application ID.

You can use either sysadmin or use some user who has all the above listed responsibilities.

For SYSADMIN, utilize the following query to get the respective values

select fnd.user_id ,
       fresp.responsibility_id,
       fresp.application_id
from   fnd_user fnd
,      fnd_responsibility_tl fresp
where  fnd.user_name = 'SYSADMIN'
and    fresp.responsibility_name = 'Order Management Super User';

Another option is Help > Diagnostics > Examine and get the values from $profile session values.