Unused Columns Count against 1000-column Table Limit Causing ORA-01792 on Compressed Table
(Doc ID 2259600.1)
Last updated on FEBRUARY 26, 2019
Applies to:Oracle Database - Enterprise Edition - Version 126.96.36.199 and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Information in this document applies to any platform.
Columns cannot be physically dropped from compressed tables. This is not a bug.
- If the compression type is BASIC, you will get an error: ORA-39726: unsupported add/drop column operation on compressed tables.
- If the compression type is an advanced-compression type, such as OLTP, the drop column succeeds, but internally it marks the column as unused (i.e. hidden) and does not physically drop it.
- Unused columns count against the 1000-column limit for tables in an Oracle database. The total count of columns that count against this limit can be obtained by getting a count from DBA_TAB_COLS.
A column was dropped from a table compressed with advanced table compression.
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