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Oracle 20c: Automatic Index Optimization

Starting 20c, one do not need to bother about index rebuilding, shrinking, managing them. We can automate this using feature Automatic Data Optimization option + marking the indexing to certain tier/policies.

The optimization process includes actions such as compressing, shrinking, or rebuilding the indexes:

  • Compress: Compresses portions of the key values in an index segment (~3 times)
  • Shrink: Merges the contents of index blocks where possible to free blocks for reuse
  • Rebuild: Rebuilds an index to improve space usage and access speed

How to get started

SQL> alter system set HEAT_MAP = ON;

And there are two options ,

ADD POLICY TIER in order to perform the operation on a say low cost/ tier 2 tablespace when tier 1 storage is under space pressure

ADD POLICY OPTIMIZE in order to kick off the process after a certain number of days passes without accessing the index

Some examples

  • Alter index index1 on schema.table(col1) ILM add policy optimize after 10 days of no modifications;
  • Alter index index1 ILM add policy tier tablespacename;
  • Alter index index1 on schema.table(col1) ILM add policy optimize after 5 days of no access;

License required for Advanced compression option and ADO

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