Semaphore and shared memory requirements for a DBI connection

Last Published: April 25, 2020

Solution or Workaround

How many semaphores are required for a DBI connection? How much shared memory is used by each DBI connection?


Each ArcInfo Data Base Integrator CONNECT uses one semaphore.

If two concurrent ArcInfo sessions are connected to a DBMS at the same time, two semaphores would be used by the DBI.

The system administrator should examine all the parameters dealing with semaphores when increasing the number of semaphores on the system. For example, semaphore identifiers (seminfo_semmni) should also be increased.

Each DBI channel uses 32 KB of shared memory. There is a maximum of ten channels per ArcInfo connection. Therefore, the Database Administrator should configure the kernel to allow for a maximum of 320 KB of shared memory per connection.
Consult the DBMS's technical support regarding the semaphore and shared memory requirements of the DBMS. The DBMS vendor should also be consulted for advice on how to configure the kernal for optimum performance of the DBMS.

ArcInfo's DBI semaphore and shared memory requirements are in addition to the requirements of the DBMS. DBI requirements must be added to the semaphore and shared memory allocation recommended by the DBMS vendor.

Article ID:000001315

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