Oracle Database SQL Language Reference for additional information about the ALTER TABLESPACE command

Restoring a Hybrid Columnar Compression Table

There may be times when a Hybrid Columnar Compression table must be restored from a backup. The table can be restored to a system that supports Hybrid Columnar Compression, or to a system that does not support Hybrid Columnar Compression. When restoring a table with Hybrid Columnar Compression to a system that supports Hybrid Columnar Compression, restore the file using Oracle Recovery Manager (RMAN) as usual.

When a Hybrid Columnar Compression table is restored to a system that does not support Hybrid Columnar Compression, you must convert the table from Hybrid Columnar Compression to OLTP compression or an uncompressed format. To restore the table, do the following:

Ensure there is sufficient storage in environment to hold the data in uncompressed or OLTP compression format.

Use RMAN to restore the Hybrid Columnar Compression tablespace.

Complete one of the following actions to convert the table from Hybrid Columnar Compression to OLTP compression or an uncompressed format:

Use the following statement to change the data compression from Hybrid Columnar Compression to COMPRESS FOR OLTP:

ALTER TABLE table_name MOVE COMPRESS FOR OLTP;

Use the following statement to change the data compression from Hybrid Columnar Compression to NOCOMPRESS:

ALTER TABLE table_name MOVE NOCOMPRESS;

Use the following statement to change each partition to NOCOMPRESS:

ALTER TABLE table_name MOVE PARTITION partition_name NOCOMPRESS;

Change each partition separately.

Use the following statement to move the data to NOCOMPRESS in parallel:

ALTER TABLE table_name MOVE NOCOMPRESS PARALLEL;

See ALso:

Oracle Database Backup and Recovery User's Guide for additional information about RMAN

Oracle Database SQL Language Reference for additional information about the ALTER TABLE command

Notes and Other Restrictions for Compressed Tables

The following are notes and restrictions related to compressed tables:

Online segment shrink is not supported for compressed tables.##压缩表不支持在线segment shrink操作

The table compression methods described in this section do not apply to SecureFiles large objects (LOBs). SecureFiles LOBs have their own compression methods. See Oracle Database SecureFiles and Large Objects Developer's Guide for more information.##本节所说的压缩方式不能再SecureFiles large objects上使用，SecureFiles LOBs有自己的压缩方式

Compression technology uses CPU. Ensure that you have enough available CPU to handle the additional load.##压缩操作对cpu的消耗比较高，确保你的cpu资源够用

Tables created with basic compression have the PCT_FREE parameter automatically set to 0 unless you specify otherwise.##建表时指定basic压缩方式PCT_FREE值为0，当然你也可以特别指定其他的你认为合适的值。(建表时指定oltp压缩方式，PCT_FREE值默认会被设置为10)

Packing Compressed Tables

If you use conventional DML on a table compressed with basic compression or Hybrid Columnar Compression, then all inserted and updated rows are stored uncompressed or in a less-compressed format. To "pack" the compressed table so that these rows are compressed, use an ALTER TABLE MOVE statement. This operation takes an exclusive lock on the table, and therefore prevents any updates and loads until it completes. If this is not acceptable, then you can use online table redefinition.

See Also: