Saves the schema cache of a database to an
operating system file. Subsequent sessions can then share the same
cache by using the Schema Cache File (-cache) parameter.
Syntax
SAVE CACHE
{ CURRENT | COMPLETE }
{database-name| VALUE ( char-expr ) }
TO
{pathname| VALUE ( char-expr ) }
[ NO-ERROR ]
|
- CURRENT
- Specifies that only the portion of the schema cache that applies
to referenced tables is saved to the file. By using this option
you can tailor a small schema cache file for an application that
does not use all the tables in the database.
- COMPLETE
- Specifies that the complete schema cache for the database is
saved to the file. If you use this option, the client process builds
a complete schema cache in memory including template records and
all trigger information for every table in the database.
-
database-name
- Specifies the literal logical name of a currently connected OpenEdge database.
-
pathname
- Specifies the literal pathname of an operating system file to
hold the schema cache. In Windows, the pathname cannot contain characters outside
of the non-Unicode code page. See OpenEdge Development: Internationalizing
Applications for more information about Unicode and code
pages.
- VALUE (char-expr)
- Returns the corresponding literal database name or pathname
specified by the character expression in char-expr.
- 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 saves the complete schema cache for each database that
you specify in the current working directory, and displays any error
messages associated with connecting or saving the cache:
r-schcsh.p
DEFINE VARIABLE db-name AS CHARACTER NO-UNDO FORMAT "x(12)" INITIAL ?.
DEFINE VARIABLE icnt AS INTEGER NO-UNDO.
DO WHILE db-name <> "":
SET db-name LABEL "Database Name"
WITH FRAME A SIDE-LABELS TITLE "Save Cache" VIEW-AS DIALOG-BOX.
IF db-name <> "" THEN
CONNECT VALUE(db-name) -1 NO-ERROR.
ELSE LEAVE.
IF NOT ERROR-STATUS:ERROR THEN DO:
SAVE CACHE COMPLETE VALUE(db-name) TO VALUE(db-name + ".csh") NO-ERROR.
IF NOT ERROR-STATUS:ERROR THEN
MESSAGE "Saved schema cache for" db-name "in" db-name + ".csh.".
ELSE DO:
BELL.
DO icnt = 1 TO ERROR-STATUS:NUM-MESSAGES:
MESSAGE ERROR-STATUS:GET-MESSAGE(icnt) VIEW-AS ALERT-BOX.
END.
END.
END.
ELSE DO:
BELL.
DO icnt = 1 TO ERROR-STATUS:NUM-MESSAGES:
MESSAGE ERROR-STATUS:GET-MESSAGE(icnt) VIEW-AS ALERT-BOX.
END.
END.
DISCONNECT VALUE(db-name) NO-ERROR.
END.
|
Notes
- The
schema cache is saved to the file in a binary format that is portable
across machines.
- For information on using an existing schema cache file, see OpenEdge
Data Management: Database Administration. For information
on the Schema Cache File (-cache) startup parameter,
see OpenEdge Deployment: Startup Command and Parameter Reference.
- Any schema changes to the database make the saved cache invalid.
If the schema cache file is invalid when the AVM tries to access
it, the AVM displays a warning message, ignores the file, and reads
the required schema cache from the database.
- To set up your database environment to use the CURRENT option, you
only have to connect to the database and read from the tables that compose
the schema you want to save. This is sufficient for the SAVE CACHE
statement to save all parts of each table in the schema, including template
records and trigger information. If you want to save a different subschema
of the database, you must disconnect and then reconnect to the database
before reading the tables for that subschema.
- For a DataServer, the AVM saves the schema cache for the entire schema
holder database. You cannot save the schema cache for a non-OpenEdge database separately.
For more information on schema cache files for DataServers, see the OpenEdge DataServer
Guides (OpenEdge Data Management: DataServer for Microsoft SQL
Server and OpenEdge Data Management: DataServer for
Oracle).