Startup Options

Use the following startup options for operations with large numbers of users.

-gm

Sets the default number of connections.

 -gm #_connections_to_support

Although this represents the total number of connections the server will support, not all connections will be active at any one time.

-iqgovern

Places a ceiling on the maximum number of queries to execute at once. If more users than the -iqgovern limit have submitted queries, new queries will be queued until one of the active queries is finished.

-iqgovern #_ ACTIVE_ queries_to_support

The optimal value for -iqgovern depends on the nature of your queries, number of CPUs, and size of the Sybase IQ buffer cache. The default value is 2*numCPU + 10. With a large number of connected users, you may find that setting this option to 2*numCPU + 4 provides better throughput.

-gn

Sets the number of execution threads for the catalog store and connectivity while running with multiple users.

 -gn  number of tasks (both user
and system requests) that the database server can execute concurrently

The correct value for -gn depends on the value of -gm. The start_iq utility calculates -gn and sets it appropriately. Setting -gn too low can prevent the server from operating correctly. Setting -gn above 480 is not recommended.

-c

Sets the catalog store cache size.

 -c catalog_store_cache_size

The catalog cache size is highly dependent on schema size and the number of objects. The catalog store buffer cache is also the general memory pool for the catalog store. To specify in MB, use the form -c nM, for example, -c 64M. Sybase recommends these values:

Catalog Buffer Cache Settings
For this many users	Set -c to this minimum value or higher
up to 1000	64MB
up to 200	48MB (start_iq default for 64-bit); larger numbers of users may benefit from 64MB

-cl and -ch

Set upper (-ch) and lower (-cl) limits for the catalog store cache size.

-cl minimum cache size -ch maximum cache size

If the standard catalog cache size is too small, set -cl and -ch parameters. On 32-bit platforms, try these settings:

-cl 128M
-ch 256M

Do not use -c in the same configuration file or command line with -ch or -cl. For related information, see the -ch cache-size option.

Warning! To control catalog store cache size explicitly, you must do either of the following, but not both, in your configuration file (.cfg) or on the UNIX command line for server startup:

Set the -c parameter
Set specific upper and lower limits for the catalog store cache size using the -ch and -cl parameters

Specifying different combinations of the parameters above can produce unexpected results.

-iqmt

Sets the number of processing threads.

If -iqmt is set too low for the -gm setting, then thread starvation can occur.