*** Migration in NOARCHIVELOG mode will reduce the upgrade time and hence downtime.
NOTE: NOARCHIVELOG should NOT be used if any log-based replication technology is used. Log-based technologies include Active Data Guard, Oracle GoldenGate, XStream, Oracle Streams, Data Guard (Redo Apply and SQL Apply), Asynchronous Change Data Capture(CDC) and Audit Vault redo collector.
*** Main function of the migration is to create a new data dictionary. The upgrade can be tested for most of the migration functionality by using a copy of the databases SYSTEM tablespace and ROLLBACK SEGMENT tablespaces and marking all other tablespaces OFFLINE. This allows realistic timings to be obtained without having to copy an entire database.
*** Make all tablespaces OFFLINE NORMAL or make READ ONLY except for SYSTEM, SYSAUX (When migrating to 10gR2 or higher) and those containing rollback segments prior to migration. This way if migration fails only the SYSTEM and rollback datafiles need to be restored rather than the entire database.
Note: You must OFFLINE the TABLESPACE as migrate does not allow OFFLINE files in an ONLINE tablespace.
*** When upgrading to Oracle Database 10g, optimizer statistics are collected for dictionary tables that lack statistics. This statistics collection can be time consuming for databases with a large number of dictionary tables, but statistics gathering only occurs for those tables that lack statistics or are significantly changed during the upgrade.
To decrease the amount of downtime incurred when collecting statistics, you can collect statistics prior to performing the actual database upgrade.
Should use the DBMS_STATS.GATHER_SCHEMA_STATS procedure to gather statistics for your 9.2.0.X database.
*** Make all tablespaces OFFLINE NORMAL or make READ ONLY except for SYSTEM, SYSAUX (When migrating to 10gR2 or higher) and those containing rollback segments prior to migration. This way if migration fails only the SYSTEM and rollback datafiles need to be restored rather than the entire database.
Note: You must OFFLINE the TABLESPACE as migrate does not allow OFFLINE files in an ONLINE tablespace.
*** When upgrading to Oracle Database 10g, optimizer statistics are collected for dictionary tables that lack statistics. This statistics collection can be time consuming for databases with a large number of dictionary tables, but statistics gathering only occurs for those tables that lack statistics or are significantly changed during the upgrade.
To decrease the amount of downtime incurred when collecting statistics, you can collect statistics prior to performing the actual database upgrade.
Should use the DBMS_STATS.GATHER_SCHEMA_STATS procedure to gather statistics for your 9.2.0.X database.
To verify the schema with stale statistics, refer Note 560336.1 Script to Check Schemas with Stale Statistics
Note : Please test before upgrading production database by upgrading a test database.
Source:
Best Practices to Minimize Downtime During Upgrade [ID 455744.1]
Source:
Best Practices to Minimize Downtime During Upgrade [ID 455744.1]
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