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ORA-00020 and ASM

SYMPTOMS

An ASM instance complains of

ORA-00020: maximum number of processes (n) exceeded

CAUSE

The Oracle parameter PROCESSES has been exceeded as a result of multiple database instances connecting to the ASM instance

The default value (often 40) is insufficient to support more than one database connecting to the ASM instance

SOLUTION

Increase the PROCESSES parameter in the ASM parameter file

Processes = 25 + 15n, where n is the number of instances on the box using ASM for their storage.

NOTE : this formula is for a basic instance and does not accommodate for

* Multiple ARCH processes
* Multiple LGWR processes

Should the ORA-20 occur even after implementing this formula … add additional for any multiples of these background processes

More details about this calculation are available in the NOTE 265633.1 “ASM Technical Best Practices”

For 11.2 set up, the formula is  PROCESSES = 50 + 50*n

where n is the number database instances connecting to the Oracle ASM instance.

This is in the standard document

https://docs.oracle.com/cd/E11882_01/server.112/e18951/asminst.htm#OSTMG94080

 

For  12c set up, the formulas are

For n < 10, PROCESSES = 50*n + 50

For n >= 10, PROCESSES = 10*n + 450

This is in the standard document

https://docs.oracle.com/database/121/OSTMG/GUID-3C096558-27B8-4EAF-A61C-892CBDD7E7F7.htm

 

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