MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 21: ODBC API Reference


 

SQLSetEnvAttr

Conformance

Version Introduced: ODBC 3.0
Standards Compliance: ISO 92

Summary

SQLSetEnvAttr sets attributes that govern aspects of environments.

Syntax

SQLRETURN SQLSetEnvAttr(
     SQLHENV     EnvironmentHandle,
     SQLINTEGER     Attribute,
     SQLPOINTER     ValuePtr,
     SQLINTEGER     StringLength);

Arguments

EnvironmentHandle

[Input]
Environment handle.

Attribute

[Input]
Attribute to set, listed in "Comments."

ValuePtr

[Input]
Pointer to the value to be associated with Attribute. Depending on the value of Attribute, ValuePtr will be a 32-bit integer value or point to a null-terminated character string.

StringLength

[Input] If ValuePtr points to a character string or a binary buffer, this argument should be the length of *ValuePtr. If ValuePtr is an integer, StringLength is ignored.

Returns

SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_ERROR, or SQL_INVALID_HANDLE.

Diagnostics

When SQLSetEnvAttr returns SQL_ERROR or SQL_SUCCESS_WITH_INFO, an associated SQLSTATE value can be obtained by calling SQLGetDiagRec with a HandleType of SQL_HANDLE_ENV and a Handle of EnvironmentHandle. The following table lists the SQLSTATE values commonly returned by SQLSetEnvAttr and explains each one in the context of this function; the notation "(DM)" precedes the descriptions of SQLSTATEs returned by the Driver Manager. The return code associated with each SQLSTATE value is SQL_ERROR, unless noted otherwise. If a driver does not support an environment attribute, the error can be returned only during connect time.

SQLSTATE Error Description
01000 General warning Driver-specific informational message. (Function returns SQL_SUCCESS_WITH_INFO.)
01S02 Option value changed The driver did not support the value specified in ValuePtr and substituted a similar value. (Function returns SQL_SUCCESS_WITH_INFO.)
HY000 General error An error occurred for which there was no specific SQLSTATE and for which no implementation-specific SQLSTATE was defined. The error message returned by SQLGetDiagRec in the *MessageText buffer describes the error and its cause.
HY001 Memory allocation
error		 The driver was unable to allocate memory required to support execution or completion of the function.
HY009 Invalid use of null pointer The Attribute argument identified an environment attribute that required a string value, and the ValuePtr argument was a null pointer.
HY010 Function sequence error (DM) A connection handle has been allocated on EnvironmentHandle.
HY013 Memory management error The function call could not be processed because the underlying memory objects could not be accessed, possibly because of low memory conditions.
HY024 Invalid attribute value Given the specified Attribute value, an invalid value was specified in ValuePtr.
HY090 Invalid string or buffer length The StringLength argument was less than 0 but was not SQL_NTS.
HY092 Invalid attribute/option identifier (DM) The value specified for the argument Attribute was not valid for the version of ODBC supported by the driver.
HYC00 Optional feature not implemented The value specified for the argument Attribute was a valid ODBC environment attribute for the version of ODBC supported by the driver, but was not supported by the driver.

(DM) The Attribute argument was SQL_ATTR_OUTPUT_NTS, and ValuePtr was SQL_FALSE.

Comments

An application can call SQLSetEnvAttr only if no connection handle is allocated on the environment. All environment attributes successfully set by the application for the environment persist until SQLFreeHandle is called on the environment. More than one environment handle can be allocated simultaneously in ODBC 3.x.

The format of information set through ValuePtr depends on the specified Attribute. SQLSetEnvAttr will accept attribute information in one of two different formats: a null-terminated character string or a 32-bit integer value. The format of each is noted in the attribute's description.

There are no driver-specific environment attributes.

Connection attributes cannot be set by a call to SQLSetEnvAttr. Attempting to do so will return SQLSTATE HY092 (Invalid attribute/option identifier).

Attribute ValuePtr contents
SQL_ATTR_CONNECTION_POOLING
(ODBC 3.0)		 A 32-bit SQLUINTEGER value that enables or disables connection pooling at the environment level. The following values are used:

SQL_CP_OFF = Connection pooling is turned off. This is the default.

SQL_CP_ONE_PER_DRIVER = A single connection pool is supported for each driver. Every connection in a pool is associated with one driver.

SQL_CP_ONE_PER_HENV = A single connection pool is supported for each environment. Every connection in a pool is associated with one environment.

Connection pooling is enabled by calling SQLSetEnvAttr to set the SQL_ATTR_CONNECTION_POOLING attribute to SQL_CP_ONE_PER_DRIVER or SQL_CP_ONE_PER_HENV. This call must be made before the application allocates the shared environment for which connection pooling is to be enabled. The environment handle in the call to SQLSetEnvAttr is set to null, which makes SQL_ATTR_CONNECTION_POOLING a process-level attribute. After connection pooling is enabled, the application then allocates an implicit shared environment by calling SQLAllocHandle with the InputHandle argument set to SQL_HANDLE_ENV.

After connection pooling has been enabled and a shared environment has been selected for an application, SQL_ATTR_CONNECTION_POOLING cannot be reset for that environment, because SQLSetEnvAttr is called with a null environment handle when setting this attribute. If this attribute is set while connection pooling is already enabled on a shared environment, the attribute affects only shared environments that are allocated subsequently.

For more information, see "ODBC Connection Pooling" in Chapter 6, "Connecting to a Data Source or Driver."
SQL_ATTR_CP_MATCH
(ODBC 3.0)		 A 32-bit SQLUINTEGER value that determines how a connection is chosen from a connection pool. When SQLConnect or SQLDriverConnect is called, the Driver Manager determines which connection is reused from the pool. The Driver Manager attempts to match the connection options in the call and the connection attributes set by the application to the keywords and connection attributes of the connections in the pool. The value of this attribute determines the level of precision of the matching criteria.

The following values are used to set the value of this attribute:

SQL_CP_STRICT_MATCH = Only connections that exactly match the connection options in the call and the connection attributes set by the application are reused. This is the default.

SQL_CP_RELAXED_MATCH = Connections with matching connection string keywords can be used. Keywords must match, but not all connection attributes must match.

For more information on how the Driver Manager performs the match in connecting to a pooled connection, see SQLConnect. For more information on connection pooling, see "ODBC Connection Pooling" in Chapter 6, "Connecting to a Data Source or Driver."
SQL_ATTR_ODBC_VERSION
(ODBC 3.0)		 A 32-bit integer that determines whether certain functionality exhibits ODBC 2.x behavior or ODBC 3.x behavior. The following values are used to set the value of this attribute:

SQL_OV_ODBC3 = The Driver Manager and driver exhibit the following ODBC 3.x behavior:

  • The driver returns and expects ODBC 3.x codes for date, time, and timestamp.

  • The driver returns ODBC 3.x SQLSTATE codes when SQLError, SQLGetDiagField, or SQLGetDiagRec is called.

  • The CatalogName argument in a call to SQLTables accepts a search pattern.

SQL_OV_ODBC2 = The Driver Manager and driver exhibit the following ODBC 2.x behavior. This is especially useful for an ODBC 2.x application working with an ODBC 3.x driver.

  • The driver returns and expects ODBC 2.x codes for date, time, and timestamp.

  • The driver returns ODBC 2.x SQLSTATE codes when SQLError, SQLGetDiagField, or SQLGetDiagRec is called.

  • The CatalogName argument in a call to SQLTables does not accept a search pattern.

An application must set this environment attribute before calling any function that has an SQLHENV argument, or the call will return SQLSTATE HY010 (Function sequence error).

For more information, see "Declaring the Application's ODBC Version" in Chapter 6, "Connecting to a Data Source or Driver" and "Behavioral Changes" in Chapter 17, "Programming Considerations."

    SQL_ATTR_OUTPUT_NTS
    (ODBC 3.0)    		 A 32-bit integer that determines how the driver returns string data. If SQL_TRUE, the driver returns string data null-terminated. If SQL_FALSE, the driver does not return string data null-terminated.

    This attribute defaults to SQL_TRUE. A call to SQLSetEnvAttr to set it to SQL_TRUE returns SQL_SUCCESS. A call to SQLSetEnvAttr to set it to SQL_FALSE returns SQL_ERROR and SQLSTATE HYC00 (Optional feature not implemented).

    Related Functions

    For information about See
    Allocating a handle SQLAllocHandle
    Returning the setting of an environment attribute SQLGetEnvAttr