Activating the Natural Buffer Pool on Linux

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# Activating the Natural Buffer Pool on Linux

This document covers the following topics:

- General Information

- Changing the Kernel Parameters

## General Information

Since the Natural buffer pool requires resources that should be created every time your system is booted, a procedure to activate the buffer pool should be called during system startup.

The Natural installation process provides a buffer pool start/stop service procedure. The name of the procedure will be generated depending on the installation directory.

Furthermore, the Natural installation process determines the platform automatically and prepares the system to execute the start/stop service procedure during start/stop of the system. Depending on the platform, the system directory for initialization and, if needed, the runlevel startup directories will be selected. The start/stop service procedure will be copied to the system directory for initialization and links will be created in the runlevel startup directories or it will create the unit files for systemd.

The Natural installation process installs the buffer pool start/stop service when sudoers permissions are available.

You can also use the script daemon.sh in the <install-dir>/common/bin directory (see also the documentation Installing Software AG Products, section Register Daemons to Automatically Start and Shut Down Products on Linux Systems). The used rc scripts are in <install-dir>/Natural/INSTALL/sys.

The Natural buffer pool needs some operating system resources for its operation. Therefore, kernel parameters need to be checked and, if necessary, increased as described below.

To verify the operation of the buffer pool, invoke the `NATBPMON` utility which is used to monitor the buffer pool's activity.

## Changing the Kernel Parameters

The information below applies to Linux.

The Natural buffer pool needs the following operating system resources for its operation:

- A set of semaphores to enable synchronization between the users.

- Shared memory to store the buffer pools objects.

The amount of available shared memory and the semaphores are configured in the kernel. For information on how to change your current kernel, contact your system administrator or consult your respective operating system documentation.

Note
Since semaphores are also needed to synchronize the access to Natural system files, additional operating system resources should also be considered here.

The following abbreviations are used:

NBP | Number of buffer pools running on one computer.
SMU | Sum of all "maximum users" assignments for all buffer pools.
MAXMEM | Largest buffer pool size value for all buffer pools.
NSF | Number of system files used.

If you have only one buffer pool on your computer, the following values are used:

NBP | 1
SMU | "Maximum users" assignment from the buffer pool assignments in the local configuration file.
MAXMEM | Buffer pool size from the buffer pool assignments in the local configuration file.

As not all resources defined by the default parameter settings are used during normal system operation, the default values are sufficient to operate one buffer pool supporting up to 20 users using about 1 MB of memory.

Note
You can find the default values specific to your environment in your kernel configuration file. Do not decrement any kernel parameters that are above their default values, as other software may need the larger value.

Change the following kernel parameters to the required values as follows:

Name | Required Value
--- | ---
`SEMAEM` * | Must be at least SMU.
`SEMMNI` | Increment by (NBP + NSF).
`SEMMNS` | Increment by (SMU + 5 * NBP) + NSF.
`SEMMNU` * | Increment by SMU.
`SEMMSL` | Must be at least SMU + 4.
`SEMUME` * | Must be at least 5.
`SEMVMX` * | Must be at least SMU.
`SHMMAX` | Must be at least MAXMEM.
`SHMMNI` | Increment by NBP.
`SHMSEG` | Must be at least 4.

* Cannot be modified on Linux.

Review the changes made to the file sag1natbpsrv in your init.d directory in case the startup message is not displayed during rebooting.

Note
If the system should fail to boot after modification (that is, the new kernel cannot be booted), check if there is an error in the startup procedure. Detailed information about trouble-shooting the operating system can be found in your respective operating system manuals. If you cannot solve the problem, contact Software AG support.

### On this page

- General Information
- Changing the Kernel Parameters