DISCONNECT statement

Disconnects the specified database.

Syntax 

 

DISCONNECT { logical-name | VALUE ( expression ) } [ NO-ERROR ]

logical-name

A logical database name. It can be an unquoted string or a quoted string. The logical-name is previously set, at startup or with a CONNECT statement, by using the Logical Database Name (-ld) parameter. If a logical name was not specified using the -ld parameter, then the physical database filename, without the .db suffix, is the default logical name.

VALUE (expression)

A character-string expression that evaluates to a logical database name.

NO-ERROR

Suppresses ABL errors or error messages that would otherwise occur and diverts them to the ERROR-STATUS system handle. If an error occurs, the action of the statement is not done and execution continues with the next statement. If the statement fails, any persistent side-effects of the statement are backed out. If the statement includes an expression that contains other executable elements, like methods, the work performed by these elements may or may not be done, depending on the order the AVM resolves the expression elements and the occurrence of the error.

To check for errors after a statement that uses the NO-ERROR option:

Check the ERROR-STATUS:ERROR attribute to see if the AVM raised the ERROR condition.

Check if the ERROR-STATUS:NUM-MESSAGES attribute is greater than zero to see if the AVM generated error messages. ABL handle methods used in a block without a CATCH end block treat errors as warnings and do not raise ERROR, do not set the ERROR-STATUS:ERROR attribute, but do add messages to the ERROR-STATUS system handle. Therefore, this test is the better test for code using handle methods without CATCH end blocks. ABL handle methods used in a block with a CATCH end block raise ERROR and add messages to the error object generated by the AVM. In this case, the AVM does not update the ERROR-STATUS system handle.

Use ERROR-STATUS:GET-MESSAGE( message-num ) to retrieve a particular message, where message-num is 1 for the first message.

If the statement does not include the NO-ERROR option, you can use a CATCH end block to handle errors raised by the statement.

Some other important usage notes on the NO-ERROR option:

NO-ERROR does not suppress errors that raise the STOP or QUIT condition.

A CATCH statement, which introduces a CATCH end block, is analogous to a NO-ERROR option in that it also suppresses errors, but it does so for an entire block of code. It is different in that the error messages are contained in a class-based error object (generated by the AVM or explicitly thrown), as opposed to the ERROR-STATUS system handle. Also, if errors raised in the block are not handled by a compatible CATCH block, ON ERROR phrase, or UNDO statement, then the error is not suppressed, but handled with the default error processing for that block type.

When a statement contains the NO-ERROR option and resides in a block with a CATCH end block, the NO-ERROR option takes precedence over the CATCH block. That is, an error raised on the statement with the NO-ERROR option will not be handled by a compatible CATCH end block. The error is redirected to the ERROR-STATUS system handle as normal.

If an error object is thrown to a statement that includes the NO-ERROR option, then the information and messages in the error object will be used to set the ERROR-STATUS system handle. This interoperability feature is important for those integrating code that uses the traditional NO-ERROR technique with the newer, structured error handling that features error objects and CATCH end blocks.

Example 

This procedure disconnects the database with logical name mydb:

 

r-discnt.p

DISCONNECT mydb.

Notes 

By default, the AVM disconnects all databases at the end of a session. The DISCONNECT statement, which explicitly disconnects a database, does not execute until all active procedures that reference the database end or stop.

If a transaction is active for logical-name, DISCONNECT is deferred until the transaction completes or is undone. If a CONNECT statement for the same logical-name database is executed before the same transaction completes or is undone, then the pending CONNECT and DISCONNECT cancel each other and the database remains connected.

When the database referred to by logical-name is disconnected, existing aliases for logical-name remain in existence. Later, if you connect to a database with the same logical-name, the same alias is still available.

See also 

ALIAS function, CONNECT statement, CONNECTED function, CREATE ALIAS statement, CREATE CALL statement, DATASERVERS function, DBCODEPAGE function, DBCOLLATION function, DBRESTRICTIONS function, DBTYPE function, DBVERSION function, DELETE ALIAS statement, FRAME-DB function, LDBNAME function, NUM-DBS function, PDBNAME function, SDBNAME function