Oracle 参数 DST_UPGRADE_INSERT_CONV 官方解释，作用，如何配置最优化建议
本站中文解释
DST_UPGRADE_INSERT_CONV参数用于控制当数据库由9i升级到10g时，是否启用时间戳断续性升级功能，当参数设置为TRUE时表示启用，默认值为TRUE，可以在系统级和会话级设置，该参数主要用于避免10g中新特性DST秒跳，当时间拨转时有数据可能会受到影响，而该参数可以让9i系统对时间断续性进行插入操作。 因此，要设置正确的DST_UPGRADE_INSERT_CONV参数，在升级到10g时，需将参数设置为TRUE。
官方英文解释
DST_UPGRADE_INSERT_CONV specifies whether internal operators will be allocated on top of TIMESTAMP WITH TIME ZONE (TSTZ) columns of tables which have not been upgraded during the upgrade window of daylight saving time patching for TIMESTAMP WITH TIME ZONE data.
| Property | Description |
|---|---|
|
Parameter type |
Boolean |
|
Default value |
|
|
Modifiable |
|
|
Modifiable in a PDB |
Yes |
|
Range of values |
|
|
Basic |
No |
Values
-
trueInternal operators will be allocated on top of TSTZ columns of tables which have not been upgraded. This is the default.
-
falseInternal operators will not be allocated on top of TSTZ columns of tables which have not been upgraded.
When DST_UPGRADE_INSERT_CONV is set to true during the upgrade window of the daylight saving time patching process:
-
SELECTqueries on tables with TSTZ data which have not been upgraded will use internal operators on top of TSTZ columns to present TSTZ data as if they were recorded using the new time zone translation rules. -
DML on tables with TSTZ data which have not been upgraded will use internal operators on top of TSTZ columns to ensure that the TSTZ data is recorded using the old time zone translation rules in order to be consistent with the existing TSTZ data in the same tables.
Note:
Oracle strongly recommends that this parameter is set to true throughout the upgrade window of the daylight saving time patching process. This parameter reduces the performance impact since indexes on TSTZ columns will be disabled whenever internal operators are allocated. If the parameter is set to false, then indexes will be used and this may affect performance of queries against TSTZ data during the DST upgrade window. Turning off this parameter during the upgrade window may corrupt data on disk when DMLs occur for tables with TSTZ data which have not yet been upgraded.
See Also:
Oracle Database
Globalization Support Guide for more information about this parameter
