How to find out CPU and memory usage for an instance?

Question

Hi DBA Gurus,
How to find out CPU usage and memory usage for an instance?
Any information is appreciated!
Thank you!
Robert

Answer 1

you can calculate cpu usage by adding fallowing three factors which you can get from v$sysstat
1. Parse CPU time : This represents the percentage of CPU time spent parsing SQL statements. Parse time CPU can be a strong indication that an application has not been well tuned. High parse time CPU usually indicates that the application may be spending too much time opening and closing cursors or is not using bind variables.
2. Recursive CPU time : Sometimes, to execute a SQL statement issued by a user, the Oracle Server must issue additional statements. Such statements are called recursive calls or recursive SQL statements. For example, if you insert a row into a table that does not have enough space to hold that row, the Oracle Server makes recursive calls to allocate the space dynamically if dictionary managed tablespaces are being used.
Recursive calls are also generated due to the inavailability of dictionary info in the dictionary cache, firing of database triggers, execution of DDL, execution of SQL within PL/SQL blocks, functions or stored procedures and enforcement of referential integrity constraints
3. Other CPU time : This represents the percentage of time spent looking for buffers, fetching rows or index keys, etc. Generally, \"Other\" CPU should represent the highest percentage of CPU time out of the total CPU time used.
total memory used you can calculate adding
total_agrigate_area+sga
memory usage on os level you can know by fallowing commands
vmstat 5 20 depending upon os