Disconnects the specified database.
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
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
