Using SAS Engines

Engine/Host Options for the V9, V8, and V7 Engines

These engines provide several engine/host options that control the creating and access of SAS data sets. Most of the following options correspond to options that are available through OpenVMS Record Management Services (RMS).

You can use the following engine/host options with the V9, V8, and V7 engines:

ALQ=

specifies the number of OpenVMS disk blocks to allocate initially to a data set when it is created. The value can range from 0 to 2,147,483,647. If the value is 0, the minimum number of blocks that is required for a sequential file is used. OpenVMS RMS always rounds the value up to the next disk cluster boundary.

The ALQ= option (allocation quantity) corresponds to the FAB$L_ALQ field in OpenVMS RMS. For additional details, see ALQ= Data Set Option: OpenVMS and Guide to OpenVMS File Applications.

ALQMULT=

specifies the number of pages that are preallocated to a file when it is created. The value can range from 1 to 128. The default value is 10. The ALQMULT= option is related to the ALQ= option.

For additional details, see ALQMULT= Data Set Option: OpenVMS.

BUFSIZE=

specifies the size of the internal I/O buffer used for output data sets. The value can range from 0 to the maximum allowed under OpenVMS. The engine tries to use a value in the range of 8,192 to 32,768 if possible. The BUFSIZE= option must be specified in increments of 512.

For additional details, see BUFSIZE= Data Set Option: OpenVMS.

CACHENUM=

specifies the number of I/O data caches used per SAS file. The value can range from 1 to 16. The default value is 5. The CACHENUM= option is used with the CACHESIZE= option.

For additional details, see CACHENUM= Data Set Option: OpenVMS.

CACHESIZE=

controls the size (in bytes) of the data cache used to buffer I/O pages. The value can range from 0 to the maximum allowed under OpenVMS. By default, the chosen value is an even multiple of the file's page size. A value of 0 specifies to use no data cache. Memory is consumed for the data cache, and multiple caches can be used for each data set opened. The disadvantage of large CACHESIZE= values is large consumption of memory. The advantage of large CACHESIZE= values is a reduction in the number of I/Os required to read from or write to a file.

The CACHESIZE= and BUFSIZE= options are similar, but they have important differences. The BUFSIZE= option specifies the file's page size, which is permanent. It can be set only on file creation. The CACHESIZE= option is the size of the internal memory cache used for the duration of the current open, so it can change any time the file is opened. Also, BUFSIZE= cannot be used as an engine/host option; it is valid only as a data set option.

For additional details, see CACHESIZE= Data Set Option: OpenVMS.

CNTLLEV=

specifies the level of shared access allowed to SAS data sets. Users can be given both READ and WRITE access to a data set that is opened for input only. By default, only shared READ access is allowed.

For additional details, see CNTLLEV= Data Set Option: OpenVMS.

DEQ=

specifies the number of OpenVMS disk blocks to add each time OpenVMS RMS automatically extends a data set during a write operation. The value can range from 0 to 65,535. OpenVMS RMS always rounds the value up to the next disk cluster boundary. A large value can result in fewer file extensions over the life of the file; a small value results in numerous file extensions over the life of the file. A file with numerous file extensions that might be noncontiguous slows record access.

If the value specified is 0, OpenVMS RMS uses the default value for the process.

The DEQ= option (default file extension quantity) corresponds to the FAB$W_DEQ field in OpenVMS RMS. For additional details, see DEQ= Data Set Option: OpenVMS and Guide to OpenVMS File Applications.

DEQMULT=

specifies the number of pages to extend a SAS file. The value can range from 1 to 128. The default value is 5.

For additional details, see DEQMULT= Data Set Option: OpenVMS.

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