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This article is about how to adjust the parameter process error ORA-27154,ORA-27300,ORA-27301,ORA-27302. Xiaobian thinks it is quite practical, so share it with everyone for reference. Let's follow Xiaobian and have a look.

ORA-27154,ORA-27300,ORA-27301,ORA-27302: failure occurred at: sskgpcreates

ORA-27154: post/wait create failed

ORA-27300: OS system dependent operation:semget failed with status: 28

ORA-27301: OS failure message: No space left on device

ORA-27302: failure occurred at: sskgpcreates

Look at the prompt, you will mistakenly think that there is insufficient disk space (No space left on device), but look carefully at the last prompt (generally the last error is the root cause), and find that it is a semaphore parameter setting problem.

kernel.sem = semmsl semmns semopm semmni

/etc/sysctl.conf was adjusted to

kernel.sem =250 32000 100 128

modified to

kernel.sem =250 32000 100 300

Problem solved.

Understanding of process and session:

The number of ORACLE sessions is related to the number of processes in its parameter file, and their relationship is as follows:

sessions=(1.1*process+5)

But when we increase the number of processes, the database often fails to start. This is because we also missed one unix system parameter: semmns in/etc/system/, which is the unix system semaphore parameter. Each process consumes a semaphore. After semmns is adjusted, you need to restart the unix operating system for the parameters to take effect.

However, its size is limited by hardware memory or ORACLE SGA. The range may vary from 200 to 2000.

Semmns is calculated as:

SEMMNS>processes+instance_processes+system

processes: Value of database parameter processes

instance_processes：5(smon,pmon,dbwr,lgwr,arch)

system: semaphore occupied by the system.

The semaphore occupied by the system can be found by the following command:

#ipcs -sb

The column NSEMS displays the amount of semaphore occupied by the system and some other parameters related to the connection:

License_max_sessions, license_sessions_warning, etc. default to zero, i.e. no limit.

The semaphores parameter is optimized as follows:

1. Calculate the minimum total semaphorerequirements using the following formula:

2*sum (process parameters of all database instances on the system) + overhead for background processes + system and other applications.

2. Set semmns (total semaphores systemwide)to this total.

3. Set semmsl (semaphores for each set ) to 256

4. Set semmni (total semaphores sets) tosemmns devided by semmsl, rounded up to the nearest multiple of 1024

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