Identifying Segments Nearing Maximum Extents in Oracle Database

Identify Oracle Database Segments Nearing Their Maximum Extent Limit

Sample SQL Command

 1col	segment_name format a40
 2select	owner
 3,	segment_type
 4,	segment_name
 5,	max_extents - extents as "spare"
 6,	max_extents
 7from	dba_segments
 8where	owner not in ('SYS','SYSTEM')
 9and	(max_extents - extents) < 10
10order by 4

Sample Oracle Output:


  • To proactively monitor segments approaching potential space exhaustion, allowing for timely intervention and preventing performance issues or errors.


  1. col segment_name format a40: Sets the display width for the "segment_name" column for better readability.
  2. select owner, segment_type, segment_name, max_extents - extents as "spare", max_extents: This clause selects five columns:
    • owner: Schema (user) owning the segment.
    • segment_type: Type of segment (TABLE, INDEX, PARTITION, etc.).
    • segment_name: Actual name of the segment.
    • max_extents - extents as "spare": Calculated "spare extents" remaining before reaching the limit.
    • max_extents: Maximum number of extents allowed for the segment.
  3. from dba_segments: Specifies the data source as the dba_segments system view, containing information about all database segments.
  4. where owner not in ('SYS','SYSTEM'): Excludes system-owned segments (SYS and SYSTEM) from the results.
  5. and (max_extents - extents) < 10: Filters for segments with fewer than 10 "spare extents" remaining.
  6. order by 4: Sorts the output by the calculated "spare extents" in ascending order (segments closest to limit shown first).

Key Points:

  • This code requires appropriate privileges to access dba_segments (typically DBA or SYSDBA).
  • The threshold of 10 "spare extents" can be adjusted based on your specific risk tolerance and desired early warning level.
  • The code identifies potential future issues but doesn't automatically take any action. Consider follow-up steps like analyzing space usage, increasing extents, or reorganizing data.
  • Be cautious when modifying max_extents values, as exceeding them can lead to errors and data loss.

Insights and Explanations:

  • Monitoring "spare extents" helps anticipate potential space exhaustion scenarios and allows for proactive management to avoid disruptions.
  • Understanding the factors affecting segment growth (data volume, indexes, operations) is crucial for accurate risk assessment and mitigation strategies.
  • Consider combining this code with other metrics like segment growth rate or space allocation patterns for a more comprehensive view of space usage.

Remember to use this code responsibly, understand its limitations, and adapt it to your specific database environment and risk management needs.

Posts in this Series