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Changing table index maxextents unlimited

Oracle Database Tips by Donald Burleson

Having a small value for maxextents for tables and indexes can cause unplanned outages and many DBA's set all objects to "maxextents unlimited", and all data files to "autoxtend on" (the default with later releases of Oracle).

There are two schools of thought on maxextents unlimited:

  • Don't risk lock-up - Tables should be free to grow ad-infinitum, and the DBA should never risk an unplanned outage by having a table reach max extents.

  • Lock a rapidly-growing table - A table might have an out-of-control insert, and the DBA wants to have the table lock-up.

I believe that it is an Oracle best practice to use "maxextents unlimited" and "autoextend on", thereby pushing the space management to the OS filesystem level.  You can easily manage the filesystems with Linux/Windows monitoring and alert whenever an object is taking too-frequent extents.

If you accidentally create objects with a small integer value for maxextents and you want to use "maxextents unlimited", you can use the following dictionary script to change all tables and indexes to alter then to "maxextents unlimited":

spool runme.sql
   'alter '||
   ' '||
   ' storage (maxextents unlimited);'
   object_type in ('TABLE','INDEX')
and owner = 'XXX';
spool off

For a permanent fix for maxextents unlimited, change the tablespace default for new objects to maxextents unlimited (viewed in the dba_tablespaces max_extents column):

alter tablespace
storage (maxextents unlimited);




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