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Oracle Redo log Statistics

Redo Start 
select * from v$sysstart 
where name 
in (
  'redo blocks written',
  'redo buffer allocation retries',
  'redo log space wait time')
;

Redo_blocks_written The foremost statistic is the 'redo blocks written' value.This is most useful for finding how much redo is generated for an operation or time interval.
Redo_log_space_wait_time This indicates the time the user processes had to wait to get space in the redo file.
Redo_buffer_allocation_retries This indicates the number of repeated attempts to allocate space in the redo buffer. A value indicates that the redo writer is falling behind possibly due to a log switch. Although log switch is a normal event, frequent log switches indicate improper sizing of the redo log files.

Viewing Space Usage for Temporary Tablespaces

The DBA_TEMP_FREE_SPACE dictionary view contains information about space usage for each temporary tablespace. The information includes the space allocated and the free space. You can query this view for these statistics using the following command. 

SELECT * from DBA_TEMP_FREE_SPACE;
TABLESPACE_NAME TABLESPACE_SIZE ALLOCATED_SPACE FREE_SPACE
----------------------------------- --------------- --------------- ----------
TEMP 250609664 250609664 249561088