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PREVIEW
Checks for errors that might occur during the migration of the
DBEnvironment that would cause the migration to fail. PREVIEW checks for
as many errors as it can before a migration, but it does not perform a
"test migration." It is still possible for the migration to fail after a
preview, but usually this would only occur if the DBEnvironment is
corrupt.
Scope
SQLMigrate Only
SQLMigrate Syntax
PREVIEW 'DBEnvironmentName' {FORWARD [TO 'Version']};
{BACKWARD TO'Version' }
Parameters
DBEnvironmentName identifies the DBEnvironment to be previewed.
Version indicates the version number to which you want to
migrate your DBEnvironment. Version is optional in
a forward preview. The default is to preview the
DBEnvironment against the most recent version
supported by SQLMigrate. Version must be indicated
for a backward preview. Use the SHOW VERSIONS
command to determine the value that may be entered
as the version parameter to PREVIEW the migration
of a DBEnvironment to the desired release of
ALLBASE/SQL software.
Description
* The amount of free pages left in the SYSTEM DBEFileSet is
calculated. If migration cannot be accomplished because there is
not enough space, an error is returned along with an estimate of
the additional number of pages needed.
* The PREVIEW BACKWARD command checks for database objects which
contain functionality that is not supported under an old release.
If they are detected, a warning message is issued that the
database objects will be dropped during the migration process.
You may want to save your table by issuing an ISQL UNLOAD command
before migrating your DBEnvironment.
* The PREVIEW command is not a read only operation. If the PREVIEW
command fails it may leave the DBEnvironment in an inconsistent
state. Should the PREVIEW command fail, the DBEnvironment backup
must be restored before the DBEnvironment can be accessed.
Authorization
You must be the DBECreator or have SM capability to use the PREVIEW
command.
Example 1
In the example below, a forward preview is shown. The warning is always
given as a reminder to back up your DBEnvironment. The error indicates
that there is not enough space for the migration to occur.
SQLMIGRATE=> preview 'PartsDBE' forward to 'G';.
PREVIEW BEGINNING (TUE, AUG 17, 1993, 10:12 AM)
WARNING - Before continuing, please verify that a complete backup of
the DBEnvironment exists. (DBWARN 20550)
Do you want to continue (yes,[no]) ? yes
ERROR - Insufficient space in the SYSTEM DBEFileset. (DBERR 22540)
DBEFile(s) containing 38 pages need to be added to the SYSTEM
DBEFileset before attempting the migration.
Use SQLMIGRATE to first CREATE a DBEFile, and then to ADD it to the
SYSTEM DBEFileSet. If you are concerned about the amount of additional
space being added, CREATE multiple small DBEFiles, rather than one large
one. After the migration is complete, perform an UPDATE STATISTICS on
SYSTEM.TABLE. Review SYSTEM.DBEFILE to determine the empty DBEFiles in
the SYSTEM DBEFileset, and remove them. Remember to leave about 20% of
the pages free for the temporary processing needs of ALLBASE/SQL.
PREVIEW FAILED with 1 ERROR(s) (TUE, AUG 17, 1993, 10:13 AM)
An attempt to MIGRATE this DBEnvironment will fail, and leave the
DBEnvironment in an inconsistent state. Please take corrective action
before attempting the migration.
SQLMIGRATE=>
At this point you will want to add space to the SYSTEM DBEFileSet. This
procedure is shown here:
SQLMIGRATE=> CREATE DBEFILE partsfile3 WITH PAGES = 40, NAME =`prtfile3';
The DBEFile was SUCCESSFULLY CREATED in <PartsDBE>.
SQLMIGRATE=> ADD DBEFILE partsfile3 TO DBEFILESET SYSTEM;
The DBEFile was SUCCESSFULLY ADDED in <PartsDBE>.
SQLMIGRATE=>
Issue the PREVIEW command again to make sure that no other errors will be
encountered during the migration:
SQLMIGRATE=> preview 'PartsDBE' forward to 'G';
PREVIEW BEGINNING (TUE, AUG 17, 1993, 10:13 AM)
WARNING - Before continuing, please verify that a complete backup of
the DBEnvironment exists. (DBWARN 20550)
Do you want to continue (yes,[no]) ? yes
PREVIEW SUCCEEDED with 1 WARNING(s) (TUE, AUG 17, 1993, 10:13 AM)
The proposed migration should be successful.
SQLMIGRATE=>
Example 2
In the example below, a warning is issued that a particular table will be
dropped because the column types were only supported under the current
release of ALLBASE/SQL. This table was defined under the current release
of ALLBASE/SQL and it took advantage of enhancements that exist only
under the current release. Remember that the columns that are supported
under the new release cannot be loaded into the old DBEnvironment. You
should either omit them when the unload is performed or edit the unload
file appropriately.
SQLMIGRATE=> preview 'PartsDBE' backward to 'F';
PREVIEW BEGINNING (TUE, AUG 17, 1993, 1:23 PM)
WARNING - Before continuing, please verify that a complete backup of
the DBEnvironment exists. (DBWARN 20550)
Do you want to continue (yes,[no]) ? yes
WARNING - Table PURCHDB.PARTS contains the following columns which are not
supported under the target version of ALLBASE/SQL (DBWARN
22530):
NONCASE
This table will be dropped during the migration.
Please NOTE that any other tables in your DBEnvironment that have
REFERENTIAL CONSTRAINTS on this table will also be dropped during
the migration. Please verify that a complete backup of this
DBEnvironment exists to insure that table(s) are not lost.
WARNING - View PURCHDB.PARTINFO is defined on a table or view that will be
dropped during the migration (DBWARN 22700). This view will
also be dropped. The SELECTSTRING from SYSTEM.VIEWDEF for this
view is:
SELECT PurchDB.SupplyPrice.PartNumber, PurchDB.Parts.PartName,
PurchDB.SupplyPrice.VendorNumber, PurchDB.Vendors.VendorName,
PurchDB.Supplyprice.VendPartNumber,
PurchDB.SupplyPrice.UnitPrice, PurchDB.SupplyPrice.DiscountQty
FROM PurchDB.Parts, PurchDB.SupplyPrice, PurchDB.Vendors WHERE
PurchDB.SupplyPrice.PartNumber = PurchDB.Parts.PartNumber AND
PurchDB.SupplyPrice.VendorNumber = PurchDB.Vendors.VendorNumber;
PREVIEW SUCCEEDED with 3 WARNING(s) (TUE, AUG 17, 1993, 1:23 PM)
The proposed migration should be successful.
SQLMIGRATE=>