How to find how much memory used by particular procedure or function.

Question

Hi,
How can we find out memory used by particular procedure or function?
If procedure or function is called many times in particular interver, wil it be cached in memory?
and how will it affect performance?
what type of pl/sql statement will take more time than normal sql statement?

Answer 1

Hi
There are several different memory issues to consider:
- the code itself (stored in the shared pool)
- simple variables defined in the code
- complex variables (eg VARRAY, TABLE etc)
There's a helpful note on PL/SQL profiling here - http://www.oratechinfo.co.uk/tuning.html - which mentions how to measure memory use (session PGA and UGA - that's program and user global areas)
You can find out more about shared pool memory structures here - http://download-east.oracle.com/oowsf2005/003wp.pdf.
Calling a function many times - yes, the function code will be cached (if possible). Session state (for a package) will also be retained (ie global package variables).
If many users call the same function, there will be one copy of the code but many copies of the private state.
Finally: PL/SQL statements that can take a long time include:
- anything that does heavy processing inside a tight loop;
- anything that waits (select for update; read from a pipe or dequeue from AQ etc)
Probably the most common mistake is to use PL/SQL for relational processing that can be done from SQL itself (eg writing nested PL/SQL loops to join data that could have been queried in a single SQL statement. Try to minimise context switches between PL/SQL and SQL:
- use bulk collect where possible
- use set operations in SQL
Good luck, HTH
Regards Nigel