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.Youshould use the Export and Import utilities for migration only after youhave carefully read Part I of Oracle7 Server Utilities.The Export/Import method of migration allows you to selectivelychoose tables and users to migrate.A possibly advantageous side effectof using the Export/Import method of migration is that data isautomatically compressed.Data Definition ConversionWhen importing data from one version to another version, the Importutility makes changes to data definitions as it reads in the export file.V6 V7 For example, when importing data from Version 6 to an Oracle7release, the Import utility makes the following changes to dataMigrationdefinition statements in the export file:" Columns defined as CHAR from a Version 6 export file arechanged to VARCHAR2." Users with CONNECT, RESOURCE, or DBA privileges inVersion 6 are granted the respective CONNECT, RESOURCE, orDBA roles in the Release 7.x database.Migrating Using Export/Import 5 3 " Constraints defined on tables in Version 6 are created in Release7.x, but they are initially disabled (except NOT NULLconstraints, which are enabled after import).After migration,you can manually enable these constraints as needed, using theENABLE clause of the ALTER TABLE command.The SQLsyntax for integrity constraints in Version 6 is different from thesyntax in a Release 7.x database.Import automatically adjuststhe declaration so that integrity constraints are properlyimported in a Release 7.x database (unless V6 compatibilitymode is in effect).Space Requirements for Export/ImportThe amount of space required for an export depends upon the amountof data you are exporting.Examine the views USER_SEGMENTS orDBA_SEGMENTS to determine the amount of space occupied by thedata.These views give you the number of segments allocated, but keepin mind that some segments can be allocated but unused.Refer to theOracle7 Server Administrator s Guide for more information on estimatingspace usage.Time Requirements for Export/ImportThe Export/Import method of migration may require several hours.Therefore, you may need to schedule your migration during non peak,production hours.The time required to complete a migration will, ofcourse, increase for databases that contain large amounts of data or alarge number of indexes.Note: Once an Export/Import migration has started, thedatabase being migrated is unavailable for all production tasks.5 4 Oracle7 Server Migration Step 5: Migrate the Source Database (using Export/Import)The following Export/Import steps are completely general and can beapplied to any Oracle version or release.To migrate an Oracle database using Export/Import, perform thefollowing steps:1.Export all desired objects from the original database using theExport utility shipped with the original database.Refer to Oracle7 ServerUtilities for a complete description of how to use the Export utilityfor Version 6.If you are using Version 5 of Oracle to export a Version 5database, see the following section for additional notes about theExport/Import procedure.2.Install the Oracle7, Release 7.x database.A default database may becreated in this step.If so, you can proceed to Step 4; otherwise,continue with Step 3.Additional Information: Installation of an Oracle7 release isoperating system specific.See your operating system specificOracle documentation.Read the README.DOC file includedOSDocwith your Release 7.x installation for any late additions ormodifications to the product.3.Create the Release 7.x database.All of the issues involved indatabase creation are covered thoroughly in the Oracle7 ServerAdministrator s Guide.4.Open the Release 7.x database and start an instance.From theServer Manager prompt, issue the following commands:SVRMGR> CONNECT INTERNALSVRMGR> STARTUP5.You should pre create tables, tablespace, and users in Release 7.xas necessary, for example, to improve space usage by changingstorage parameters.When you pre create tables using SQL*Plus orServer Manager, you must either run in the original databasecompatibility mode or specifically make allowances for the datadefinition conversions outlined on the previous page that occurduring import.6.Import the data and tables from the original database export usingthe Import utility shipped with Release 7.x.Refer to Oracle7 ServerUtilities for a complete description of how to use the Import utility.Migrating Using Export/Import 5 5 7.After migrating, you may discover that your tables were notimported properly.Views and synonyms may not be created in thecorrect order when dependencies exist (for example, when a viewis based on a synonym).You may have to perform one of thefollowing procedures to finish importing correctly: If all of the rows for all tables were not successfullyimported, repeat the import until it completes successfully.Be certain that IGNORE=Y and ROWS=N.IGNORE=Ycauses Import to overlook object already exists errors andROWS=N indicates that you do not want to import the rowsof table data. If some tables were imported successfully, while otherswere not even created, repeat the import with IGNORE=Nand ROWS=Y to ignore the object already exists errorsand re import the rows. If the tables had some, but not all rows imported, drop theincomplete tables and repeat the previous step.For more information on the use of the Export and Import utilities,see Oracle7 Server Utilities.If you are currently using Version 5 of Oracle (see page 1 9 in ChapterNotes for Version 51 Migration Overview), it is recommended that you upgrade first toVersion 6.If you choose to export your Version 5 files and import themdirectly to an Oracle7 release, you should be aware of the following." Column level grants are not imported and must be regrantedafter import." The EXPVEW and EXPTAB views are exported from Version 5,even though you run the DROPCAT5.SQL script prior to export.These views are not created when you perform the import to anOracle7 release.Ignore the resulting error messages.5 6 Oracle7 Server Migration C H A P T E RAfter Migrating the6Databasehis chapter discusses the steps to perform after you have completedTmigrating from one version to another version or upgrading from onerelease to another release using either the migration utility or theExport/Import method of migration.This chapter elaborates on Step 6of the migration process, discussed on page 1 5
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