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DbPool

Represents a pool of connections to a particular database configuration.

Server-side object

Implemented in

NES 3.0

To connect to a database, you first create a pool of database connections and then access individual connections as needed. For more information on the general methodology for using DbPool objects, see the Server-Side JavaScript Guide.

Created by

The DbPool constructor.

Description

The lifetime of a DbPool object (its scope) varies. Assuming it has been assigned to a variable, a DbPool object can go out of scope at different times:

It is your responsibility to release all connections and close all cursors, stored procedures, and result sets associated with a DbPool object before that object goes out of scope. Release connections and close the other objects as soon as you are done with them.

If you do not release a connection, it remains bound and is unavailable to the next user until the associated DbPool object goes out of scope. When you do call release to give up a connection, the runtime engine waits until all associated cursors, stored procedures, and result sets are closed before actually releasing the connection. Therefore, you must close those objects when you are done with them.

You can use the prototype property of the DbPool object to add a property to all DbPool instances. If you do so, that addition applies to all DbPool objects running in all applications on your server, not just in the single application that made the change. This allows you to expand the capabilities of this object for your entire server.

Property Summary      

Property Description
prototype

Allows the addition of properties to a DbPool object.

Method Summary

Method Description
connect

Connects the pool to a particular configuration of database and user.

connected

Tests whether the database pool and all of its connections are connected to a database.

connection

Retrieves an available connection from the pool.

DbPool

Creates a pool of database Connection objects and optionally connects the objects to a particular configuration of database and user.

disconnect

Disconnects all connections in the pool from the database.

majorErrorCode

Major error code returned by the database server or ODBC.

majorErrorMessage

Major error message returned by database server or ODBC. For server errors, this typically corresponds to the server's SQLCODE.

minorErrorCode

Secondary error code returned by database vendor library.

minorErrorMessage

Secondary message returned by database vendor library.

storedProcArgs

Creates a prototype for a Sybase stored procedure.

toString

Returns a string representing the specified object.

In addition, this object inherits the watch and unwatch methods from Object.


connect

Connects the pool to a particular configuration of database and user.

Method of

DbPool

Implemented in

NES 3.0

Syntax

1. connect (dbtype, serverName, username, password,
      databaseName)
2. connect (dbtype, serverName, username, password,
      databaseName[, maxConnections])
3. connect (dbtype, serverName, username, password,
      databaseName[, maxConnections[, commitflag]])

Parameters

dbtype

Database type; one of ORACLE, SYBASE, INFORMIX, DB2, or ODBC.

serverName

Name of the database server to which to connect. The server name typically is established when the database is installed and is different for different database types:

If in doubt, see your database or system administrator. For ODBC, this is the name of the ODBC service as specified in Control Panel.

userName

Name of the user to connect to the database. Some relational database management systems (RDBMS) require that this be the same as your operating system login name; others maintain their own collections of valid user names. See your system administrator if you are in doubt.

password

User's password. If the database does not require a password, use an empty string ("").

databaseName

Name of the database to connect to for the given serverName. If your database server supports the notion of multiple databases on a single server, supply the name of the database to use. If it does not, use an empty string (""). For Oracle, ODBC, and DB2, you must always use an empty string.

maxConnections

Number of connections to be created and cached in the pool. The runtime engine attempts to create as many connections as specified with this parameter. If successful, it stores those connections for later use. If you do not supply this parameter, its value is 1.

Remember that your database client license probably specifies a maximum number of connections. Do not set this parameter to a number higher than your license allows. For Sybase, you can have at most 100 connections.

If your database client library is not multithreaded, it can only support one connection at a time. In this case, your application performs as though you specified 1 for this parameter. For a current list of which database client libraries are multithreaded, see the Enterprise Server 3.0 Release Notes.

commitFlag

A Boolean value indicating whether to commit a pending transaction when the connection goes out of scope. If this parameter is false, a pending transaction is rolled back. If this parameter is true, a pending transaction if committed. For DbPool, the default value is false; for database, the default value is true. If you specify this parameter, you must also specify the maxConnections parameter.

Returns

0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.

Description

When you call this method, the runtime engine first closes and releases any currently open connections. It then reconnects the pool with the new configuration. You should be sure that all connections have been released before calling this method.

The first version of this method creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.

The second version of this method attempts to create as many connections as specified by the maxConnections parameter. If successful, it stores those connections for later use. If the runtime engine does not obtain the requested connections, it returns an error. When this connection goes out of scope, pending transactions are rolled back.

The third version of this method does everything the second version does. In addition, the commitflag parameter indicates what to do with pending transactions when this connection goes out of scope. If this parameter is false (the default), a pending transaction is rolled back. If this parameter is true, a pending transaction if committed.

Example

The following statement creates four connections to an Informix database named mydb on a server named myserver, with user name SYSTEM and password MANAGER. Pending transactions are rolled back at the end of a client request:

pool.connect("INFORMIX", "myserver", "SYSTEM", "MANAGER", "mydb", 4)

connected

Tests whether the database pool and all of its connections are connected to a database.

Method of

DbPool

Implemented in

NES 3.0

Syntax

connected()

Parameters

None.

Returns

True if the pool (and hence a particular connection in the pool) is currently connected to a database; otherwise, false.

Description

The connected method indicates whether this object is currently connected to a database.

If this method returns false for a Connection object, you cannot use any other methods of that object. You must reconnect to the database, using the DbPool object, and then get a new Connection object. Similarly, if this method returns false for the database object, you must reconnect before using other methods of that object.

Example

Example 1: The following code fragment checks to see if the connection is currently open. If it's not, it reconnects the pool and reassigns a new value to the myconn variable.

if (!myconn.connected()) {
   mypool.connect ("INFORMIX", "myserver", "SYSTEM", "MANAGER", "mydb", 4);
   myconn = mypool.connection;
}
Example 2: The following example uses an if condition to determine if an application is connected to a database server. If the application is connected, the isConnectedRoutine function runs; if the application is not connected, the isNotConnected routine runs.

if(database.connected()) {
   isConnectedRoutine() }
else {
   isNotConnectedRoutine() }

connection

Retrieves an available connection from the pool.

Method of

DbPool

Implemented in

NES 3.0

Syntax

connection (name, timeout)

Parameters

name

An arbitrary name for the connection. Primarily used for debugging.

timeout

The number of seconds to wait for an available connection before returning. The default is to wait indefinitely. If you specify this parameter, you must also specify the name parameter.

Returns

A new Connection object.


disconnect

Disconnects all connections in the pool from the database.

Method of

DbPool

Implemented in

NES 3.0

Syntax

disconnect()

Parameters

None.

Returns

0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.

Description

For the DbPool object, before calling the disconnect method, you must first call the release method for all connections in this database pool. Otherwise, the connection is still considered in use by the system, so the disconnect waits until all connections are released.

After disconnecting from a database, the only methods of this object you can use are connect and connected.

Examples

The following example uses an if condition to determine if an application is connected to a database server. If the application is connected, the application calls the disconnect method; if the application is not connected, the isNotConnected routine runs.

if(database.connected()) {
   database.disconnect() }
else {
   isNotConnectedRoutine() }

DbPool

Creates a pool of database Connection objects and optionally connects the objects to a particular configuration of database and user.

Method of

DbPool

Implemented in

NES 3.0

Syntax

1. new DbPool();
2. new DbPool (dbtype, serverName, username, password,
      databaseName);
3. new DbPool (dbtype, serverName, username, password,
      databaseName[, maxConnections]);
4. new DbPool (dbtype, serverName, username, password,
      databaseName[, maxConnections[, commitflag]]);

Parameters

dbtype

Database type. One of ORACLE, SYBASE, INFORMIX, DB2, or ODBC.

serverName

Name of the database server to which to connect. The server name typically is established when the database is installed and is different for different database types:

If in doubt, see your database or system administrator. For ODBC, this is the name of the ODBC service as specified in Control Panel.

userName

Name of the user to connect to the database. Some relational database management systems (RDBMS) require that this be the same as your operating system login name; others maintain their own collections of valid user names. See your system administrator if you are in doubt.

password

User's password. If the database does not require a password, use an empty string ("").

databaseName

Name of the database to connect to for the given serverName. If your database server supports the notion of multiple databases on a single server, supply the name of the database to use. If it does not, use an empty string (""). For Oracle, ODBC, and DB2, you must always use an empty string.

maxConnections

Number of connections to be created and cached in the pool. The runtime engine attempts to create as many connections as specified with this parameter. If successful, it stores those connections for later use. If you do not supply this parameter, its value is 1.

Remember that your database client license probably specifies a maximum number of connections. Do not set this parameter to a number higher than your license allows. For Sybase, you can have at most 100 connections.

If your database client library is not multi-threaded, it can only support one connection at a time. In this case, your application performs as though you specified 1 for this parameter. For a current list of which database client libraries are multi-threaded, see the Enterprise Server 3.0 Release Notes.

commitFlag

A Boolean value indicating whether to commit a pending transaction when the connection is released or the object is finalized.

(If the transaction is on a single page, the object is finalized at the end of the page. If the transaction spans multiple pages, the object is finalized when the connection returns to the pool.)

If this parameter is false, a pending transaction is rolled back. If this parameter is true, a pending transaction if committed. For DbPool, the default value is false; for database, the default value is true. If you specify this parameter, you must also specify the maxConnections parameter.

Description

The first version of this constructor takes no parameters. It instantiates and allocates memory for a DbPool object. This version of the constructor creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.

The second version of this constructor instantiates a DbPool object and then calls the connect method to establish a database connection. This version of the constructor also creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.

The third version of this constructor instantiates a DbPool object and then calls the connect method to establish a database connection. In addition, it attempts to create as many connections as specified by the maxConnections parameter. If successful, it stores those connections for later use. If the runtime engine does not obtain the requested connections, it returns an error. When this connection goes out of scope, pending transactions are rolled back.

The fourth version of this constructor does everything the third version does. In addition, the commitflag parameter indicates what to do with pending transactions when the connection goes out of scope. If this parameter is false (the default), a pending transaction is rolled back. If this parameter is true, a pending transaction if committed.

To detect errors, you can use the majorErrorCode method.

If possible, your application should call this constructor and make the database connection on its initial page. Doing so prevents conflicts from multiple client requests trying to manipulate the status of the connections at once.


majorErrorCode

Major error code returned by the database server or ODBC.

Method of

DbPool

Implemented in

NES 3.0

Syntax

majorErrorCode()

Parameters

None.

Returns

The result returned by this method depends on the database server being used:

Description

SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or table locking in a multi-user database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by various methods or from special properties containing error messages and codes.

Status codes are integers between 0 and 27, with 0 indicating a successful execution of the statement and other numbers indicating an error, as shown in the following table.

Table 1.3 Database status codes.  
Status code Explanation Status code Explanation

0

No error

14

Null reference parameter

1

Out of memory

15

Connection object not found

2

Object never initialized

16

Required information is missing

3

Type conversion error

17

Object cannot support multiple readers

4

Database not registered

18

Object cannot support deletions

5

Error reported by server

19

Object cannot support insertions

6

Message from server

20

Object cannot support updates

7

Error from vendor's library

21

Object cannot support updates

8

Lost connection

22

Object cannot support indices

9

End of fetch

23

Object cannot be dropped

10

Invalid use of object

24

Incorrect connection supplied

11

Column does not exist

25

Object cannot support privileges

12

Invalid positioning within object (bounds error)

26

Object cannot support cursors

13

Unsupported feature

27

Unable to open

Examples

This example updates the rentals table within a transaction. The updateRow method assigns a database status code to the statusCode variable to indicate whether the method is successful.

If updateRow succeeds, the value of statusCode is 0, and the transaction is committed. If updateRow returns a statusCode value of either five or seven, the values of majorErrorCode, majorErrorMessage, minorErrorCode, and minorErrorMessage are displayed. If statusCode is set to any other value, the errorRoutine function is called.

database.beginTransaction()
statusCode = cursor.updateRow("rentals")
if (statusCode == 0) {
   database.commitTransaction()
   }
if (statusCode == 5 || statusCode == 7) {
   write("The operation failed to complete.<BR>"
   write("Contact your system administrator with the following:<P>"
   write("The value of statusCode is " + statusCode + "<BR>")
   write("The value of majorErrorCode is " +
      database.majorErrorCode() + "<BR>")
   write("The value of majorErrorMessage is " +
      database.majorErrorMessage() + "<BR>")
   write("The value of minorErrorCode is " +
      database.minorErrorCode() + "<BR>")
   write("The value of minorErrorMessage is " +
      database.minorErrorMessage() + "<BR>")
   database.rollbackTransaction()
   }
else {
   errorRoutine()
   }

majorErrorMessage

Major error message returned by database server or ODBC. For server errors, this typically corresponds to the server's SQLCODE.

Method of

DbPool

Implemented in

NES 3.0

Syntax

majorErrorMessage()

Parameters

None.

Returns

A string describing that depends on the database server:

Description

SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or table locking in a multi-user database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by connection and DbPool methods or from special connection or DbPool properties containing error messages and codes.

Examples

See DbPool.majorErrorCode.


minorErrorCode

Secondary error code returned by database vendor library.

Method of

DbPool

Implemented in

NES 3.0

Syntax

minorErrorCode()

Parameters

None.

Returns

The result returned by this method depends on the database server:


minorErrorMessage

Secondary message returned by database vendor library.

Method of

DbPool

Implemented in

NES 3.0

Syntax

minorErrorMessage()

Parameters

None.

Returns

The string returned by this method depends on the database server:


prototype

Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.

Property of

DbPool

Implemented in

NES 2.0


storedProcArgs

Creates a prototype for a DB2, ODBC, or Sybase stored procedure.

Method of

DbPool

Implemented in

NES 3.0

Syntax

storedProcArgs (procName [, type1 [, ... typeN]])

Parameters

procName

The name of the procedure.

type1, ..., typeN

Each type is one of: "IN", "OUT", or "INOUT" Specifies the type of each parameter: input ("IN"), output ("OUT"), or both input and output ("INOUT").

Returns

Nothing.

Description

This method is only for Sybase stored procedures.

This method provides the procedure name and the parameters for that stored procedure. Sybase stored procedures can accept parameters that are only for input ("IN"), only for output ("OUT"), or for both input and output ("INOUT").

You must create one prototype for each Sybase stored procedure you use in your application. Additional prototypes for the same stored procedure are ignored.

You can specify an INOUT parameter either as an INOUT or as an OUT parameter. If you use an INOUT parameter of a stored procedure as an OUT parameter, the LiveWire Database Service implicitly passes a NULL value for that parameter.

Examples

Assume the inoutdemo stored procedure takes one input parameter and one input/output parameter, as follows:

create procedure inoutdemo ( @inparam int, @inoutparam int output)
as
if ( @inoutparam == null)
@inoutparam = @inparam + 1
else
@inoutparam = @inoutparam + 1
Assume execute the following code and then call outParameters(0), the result will be 101:

database.storedProcArgs("inoutdemo", "IN", "INOUT")
spobj= database.storedProc("inoutdemo", 6, 100);
answer = spobj.outParameters(0);
The value of answer is 101. On the other hand, assume you execute this code:

database.storedProcArgs("inoutdemo", "IN", "OUT")
spobj = database.storedProc("inoutdemo", 6, 100);
answer = spobj.outParameters(0);
In this case, the value of answer is 7.


toString

Returns a string representing the specified object.

Method of

DbPool

Implemented in

NES 3.0

Syntax

toString()

Parameters

None.

Description

Every object has a toString method that is automatically called when it is to be represented as a text value or when an object is referred to in a string concatenation.

You can use toString within your own code to convert an object into a string, and you can create your own function to be called in place of the default toString method.

This method returns a string of the following format:

db "name" "userName" "dbtype" "serverName"
where
name

The name of the database.

userName

The name of the user connected to the database.

dbType

One of ORACLE, SYBASE, INFORMIX, DB2, or ODBC.

serverName

The name of the database server.

The method displays an empty string for any of attributes whose value is unknown.

For information on defining your own toString method, see the Object.toString method.


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Last Updated: 11/13/98 10:23:04

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