Release 10.1A: OpenEdge Getting Started:
Installation and Configuration

Shared memory and kernel configuration

In OpenEdge, the multi-threaded architecture makes heavy use of file descriptors, shared memory, and semaphores. Allocation of these resources is controlled by system configuration parameters. On most systems, these parameters are set to values appropriate for OpenEdge applications. However, in some cases, one or more parameters might not be set optimally, thereby limiting the number of OpenEdge users. If you have to reset the parameters, you must reconfigure your kernel. See your operating system documentation for information on reconfiguring your operating system kernel.

The optimal parameter settings depend on the system, the application, the number of users, and some minor factors. Table 6–8 lists the crucial parameters and provides guidelines for choosing adequate values for each one.

Table 6–8: Shared memory and semaphore parameter settings 

Parameter	Meaning	Optimal setting
SHMMNI	Maximum number of shared memory (SHM) identifiers.	Current value or system default + (Total OpenEdge memory requirement)/SHMMAX.
SHMSEG	Maximum number of SHM segments a single process can attach.	4–8.
SHMALL	Maximum number of in-use SHM segments.	System default; increase if many databases are active simultaneously; decreasing -B, -n, and -L startup parameters decreases SHM requirements.
SHMMAX	Maximum SHM segment size.	System default; increase if you get OpenEdge error 1135.
SEMMNI	Number of semaphore (SEM) IDs; each represents an array of SEMs.	1 per active multi-user database.
SEMMSL	Maximum number of semaphores per SEM ID.	(Max-local-users-on-any-database + Max-#servers-on-any-database + 4).
SEMMNS	Total semaphores in the system.	(SEMMSL x #active-databases).
SEMMNU	Number of semaphore undo structures.	Same value as SEMMNS.
MAXUMEM	Maximum address space for a single user.	> = server size process + SHMSEG * SHMMAX.

The parameter settings in Table 6–8 are guidelines. Parameter values near these are acceptable in most cases, but a particular system or application might require increasing the limits.

If shared memory or semaphores are allocated incorrectly, OpenEdge displays an error message when it attempts to start an additional user or server. For example, if SEMMNS is set too low, PROSERVE fails and displays the following message:

Server: Semaphore limit exceeded Server: **The server terminated with exit code (X) (800)

Change the relevant parameter values and reconfigure the kernel in response to semaphore or shared-memory errors at startup. Table 6–9 lists the parameters that you might have to raise in response to various OpenEdge error codes.

Table 6–9: Error codes and kernel reconfiguration parameters 

Error code	Parameter to increase
1081	SEMMNU
1093	SEMMSL or SEMMNS
1130	SEMMSL
1131	SEMMNI and SEMMNS
1135	SHMMAX, MAXUMEM, and MAXUP
1137	SHMMNI
1175	SHMSEG, MAXUMEM, and MAXUP
1195	SEMMNS

Note: The Blocks in Database Buffers (-B), Lock-table Entries (-L), and Number of Users (-n) startup parameters all affect shared-memory usage. The Number of Users (-n) and Maximum Servers (-Mn) parameters affect semaphore usage (each user or server process uses one semaphore). Before reconfiguring your kernel to increase shared memory or semaphore allocation, see whether you can lower these startup values.