Calculate the Space Requirements


Sl. No.  Task         Command
1.   Undo tablespace undo_space = UNDO_RETENTION * UPS + overhead

undo_space= no. of undo blocks.

UNDO_RETENTION= UNDO_RETENTION parameter value (in seconds).

UPS= no. of undo blocks for each second.

overhead= minimal overhead for metadata (transaction tables, etc.).

SQL> 

SELECT ur.value AS undo_retention_seconds, ups.ups_blocks_per_sec, dbs.dbs_bytes, ROUND((ur.value * (ups.ups_blocks_per_sec * dbs.dbs_bytes)) / (1024*1024*1024), 2) AS undo_space_gb FROM (SELECT value FROM v$parameter WHERE name = 'undo_retention') ur,  (SELECT SUM(undoblks) / NULLIF(SUM((end_time - begin_time) * 86400), 0) AS ups_blocks_per_sec     FROM v$undostat) ups,  (SELECT block_size AS dbs_bytes     FROM dba_tablespaces     WHERE tablespace_name = (SELECT value FROM v$parameter WHERE name = 'undo_tablespace')) dbs;
2.

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