These metrics already have baseline alarms:
For I/O-related information we also have the following metrics:
· User I/O Waits - Waits for user I/O events (for example 'db file sequential read').
· Direct Writes - Number of direct writes for all cursors
· Oracle Data I/O Operations - Total number of I/O operations (both physical and logical) performed by the Oracle session.
· Oracle Physical I/O Operations - Total number of physical I/O operations (read, writes and redo) performed by the monitored Oracle instance processes.
Note that a physical I/O issued by Oracle can be satisfied by the operating system's file cache.
· DB Block Changes - The number of database blocks in memory (SGA) that were modified by the session as a result of DML activity. Such changes generate redo log entries and hence become permanent changes to the database if the transaction is committed. Because each logical change to a block typically involves more than one physical change to the block, the value of this statistic will always be considerably greater than the number of blocks dirtied in the cache.
· Physical Reads - The number of data blocks read by Oracle, which are not present in the buffer cache, thus requiring I/O read operations, i.e. the total number of data blocks read from disk.
· Physical Reads Direct - Number of reads directly from disk into the PGA, bypassing the buffer cache. Generally, these are reads from temporary segments.
· Physical Writes - Total number of data blocks written to disk. This metric represents the rate at which the monitored Oracle instance generates system I/O calls.
· Physical Writes Direct - The number of writes directly written to disk bypassing the buffer cache (as in a direct load operation).
· Sorts to Disk - Sorts which require creation of temporary segments on disk to store the intermediate sort results.
· Cache Hit Ratio - The effectiveness of the buffer cache, computed by comparing the number of block requests, which found the block in the buffer cache with the entire block requests (including requests which performed disk reads).
We should also mention that we have the following baseline alarms:
· DBO - Wait User IO Baseline - This alarm is invoked when the value of Wait User I/O has deviated from a predefined baseline.
· DBO - Physical Writes Baseline - This alarm is invoked when the value of Physical Writes has deviated from a predefined baseline.
· DBO - Physical Reads Baseline - This alarm is invoked when the value of Physical Reads has deviated from a predefined baseline.
· DBO - Cache Hit Ratio Baseline - This alarm is invoked when the value of Cache Hit Ratio has deviated from a predefined baseline
· DBO - Disk Sorts Ratio Baseline - This alarm is invoked when the value of Disk Sorts Ratio has deviated from a predefined baseline.