MAXCURS (JANUS DEFINE parameter): Difference between revisions
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<span class="pageSubtitle">MAXCURS xxx — max number of cursors allowed for a single SDS connection</span> | |||
<span class="pageSubtitle" | |||
<var>MAXCURS</var> is a parameter on [[JANUS DEFINE]], which defines and sets characteristics of a Janus port | <var>MAXCURS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port. | ||
This parameter specifies the maximum number of cursors that can be opened for a single | This parameter specifies the maximum number of cursors that can be opened for a single <var class="product">[[Media:JsdsrNew.pdf|Janus Specialty Data Store]]</var> connection. The default for <var>MAXCURS</var> is 5. | ||
A Sybase Adaptive Server or Omni SQL Server will open multiple cursors on a connection to an SDS thread. Typically, even for fairly complex requests the number of simultaneously open cursors will not exceed 3 so that the default of 5 should be fine. If a Sybase Adaptive Server attempts to open more cursors than is allowed by <var>MAXCURS</var>, the request will fail. | A <var class="product">Sybase Adaptive Server</var> or <var class="product">Omni SQL Server</var> will open multiple cursors on a connection to an SDS thread. Typically, even for fairly complex requests the number of simultaneously open cursors will not exceed 3 so that the default of 5 should be fine. If a <var class="product">Sybase Adaptive Server</var> attempts to open more cursors than is allowed by <var>MAXCURS</var>, the request will fail. | ||
The cost of having a high <var>MAXCURS</var> is the storage for each possible cursor is allocated either at port start time for each thread or at connection time for <var>[[ALLOCC (JANUS DEFINE parameter)|ALLOCC]]</var> ports. The storage required for each cursor is about 64 bytes so that on a 40 thread port with <var>MAXCURS</var> set to 5, the virtual storage used for cursor blocks would be 64*5*40 or 12,800 bytes. | The cost of having a high <var>MAXCURS</var> is the storage for each possible cursor is allocated either at port start time for each thread or at connection time for <var>[[ALLOCC (JANUS DEFINE parameter)|ALLOCC]]</var> ports. The storage required for each cursor is about 64 bytes so that on a 40 thread port with <var>MAXCURS</var> set to 5, the virtual storage used for cursor blocks would be 64*5*40, or 12,800 bytes. | ||
Valid only for SDS (also known as <var>[[JANUS DEFINE#type|OMNI]]</var> and OAS) ports. | Valid only for <var>[[JANUS DEFINE#type|SDS]]</var> (also known as <var>[[JANUS DEFINE#type|OMNI]]</var> and <var>[[JANUS DEFINE#type|OAS]]</var>) ports. | ||
== | ==See also== | ||
<ul> | |||
<li>[[List of Janus commands]] | |||
<li>[[JANUS DEFINE#parmlist|List of JANUS DEFINE parameters]] | |||
</ul> | |||
[[Category:JANUS DEFINE parameters|MAXCURS]] | [[Category:JANUS DEFINE parameters|MAXCURS]] | ||
Latest revision as of 00:33, 8 June 2016
MAXCURS xxx — max number of cursors allowed for a single SDS connection
MAXCURS is a parameter on JANUS DEFINE, which defines and sets characteristics of a Janus port.
This parameter specifies the maximum number of cursors that can be opened for a single Janus Specialty Data Store connection. The default for MAXCURS is 5.
A Sybase Adaptive Server or Omni SQL Server will open multiple cursors on a connection to an SDS thread. Typically, even for fairly complex requests the number of simultaneously open cursors will not exceed 3 so that the default of 5 should be fine. If a Sybase Adaptive Server attempts to open more cursors than is allowed by MAXCURS, the request will fail.
The cost of having a high MAXCURS is the storage for each possible cursor is allocated either at port start time for each thread or at connection time for ALLOCC ports. The storage required for each cursor is about 64 bytes so that on a 40 thread port with MAXCURS set to 5, the virtual storage used for cursor blocks would be 64*5*40, or 12,800 bytes.
Valid only for SDS (also known as OMNI and OAS) ports.