System Parameters

Introduction
Sybase Connections
System Kernel Parameters

Introduction

Your client machine should have been configured to run OPAC correctly. The correct system parameters are repeated here for information.

If you have problems with OPAC displaying blank lists or with OPACs hanging, there is a possibility that your system has been configured with insufficient number of connections to Sybase. This can be checked by typing:

sp_configure <Enter>

in isql. (Do not attempt to do this if you are not familiar with using isql). This will list a set of information, including "user connections". The value in the "run_value" column is the value your system is running; this should be set to five times the total number of users. For example, if you have 100 users, this should be set to "500".

If you believe this value to be incorrect for any reason, please contact the Help Desk.

System Kernel Parameters

Talis makes use of semaphores and shared memory, particularly in OPAC. Failure to set these system parameters correctly is likely to result in the appearance of empty lists in OPAC and core dumps on stacked searches.

Note: Users of Data General© equipment should ignore this section as their systems allocate the necessary memory dynamically.

The following parameters specifying the number of semaphore processes and shared memory segments which are going to be required should be defined in the "system" file in the /etc directory. The parameters will vary according to the number of users each machine is configured for and whether the library has enabled search stacking.

Calculating Semaphores

There are three semaphore-related parameters, the settings for which must reflect the number of users per client. For example, if you estimate that there are going to be a maximum of 100 users on each client, then the settings should be:

semsys:seminfo_semmns=100
semsys:seminfo_semmnu=100
semsys:seminfo_semmnl=100

Calculating Shared Memory

The values needing to be calculated for the parameters relating to shared memory govern the number of segments which are likely to be required by shared memory processes. These are calculated as follows:

shmsys:shminfo_shmseg

This parameter is governed by the highest number of stacked searches allowed on the system, whether by explicit or implicit stacking.

Implicit stacking includes Author crossreference searches and postrestriction searches. It is governed by the value specified for the environment variable "TAL_IMPLICIT_STACK". This variable defines the number of implicit searches which a user can stack. The default (and maximum) is 5.

Explicit stacking is governed by the value specified in the "Maximum Stacked" field within OPAC General Rules (obtained under Online Utilities, Parameters, Rules, OPAC Rules).

Take the sum of these two values (i.e. those specified against "Maximum Stacked" and "TAL_IMPLICIT_STACK") and apply the following calculation:

y = (sum of two stack parameters + 1)  3

So for example, if you have set "Maximum Stacked" to 5 and are taking the default "TAL_IMPLICIT_STACK" value of 5, this gives:

y = (5 + 5 + 1)  3 = 11 * 3 = 33

shmsys:shminfo_shmmni

This parameter is governed by the both the maximum number of users parameter (x) and the shared memory segments parameter (y), according to the following formula:

z = x  y

For example, taking the maximum number of users per client to be 100, and the shared memory segments parameter to be 33, this would give:

z = 100  33 = 3300

Amending Default Parameters in /etc/system

The steps which need to be taken are shown below.

Logon at the master console as "root".
Change directory:

cd /etc <Enter>

Take a copy of the system file by typing:

cp system system.backup <Enter>

Insert the following lines at the end of the file system, with the values adjusted to your own system as necessary. Be very careful about spelling:

set shmsys:shminfo_shmseg=33 <Enter>
set shmsys:shminfo_shmmni=3300 <Enter>
set semsys:seminfo_semmnu=100 <Enter>
set semsys:seminfo_semmns=100 <Enter>
set semsys:seminfo_semmsl=100 <Enter>

Note: TalisWeb OPAC users will need an additional parameter in this file, namely:

set shmsys:shminfo_shmmax=64000000

The value will always be 64000000. Failure to set this will result in problems trying to look at serial records in TalisWeb.

If any changes have been made to any of these values, the client machine must be rebooted at a convenient moment for these changes to take effect.