64-bit buffer

Edit online

IBM Data Virtualization Manager for z/OS introduces a 64-bit memory management model. This improves the performance and the zIIP utilization by reducing the zIIP spillover due to contention.

To customize the allocation of the 64-bit memory buffer pool, set the following parameters in the IN00 file:


Parameters	Description
SQLENGNUMSEG	This is the number of 1-megabyte (MB) segments for the main SQL engine buffers. This is the size of the main buffer. The SQLENGNUMSEG parameter controls the number of segments received on obtaining the 64-bit storage.
SQLENGNSGBF	This is the number of SQL engine main buffers to get. The SQLENGNSGBF parameter controls the number of pre-allocated 64-bit buffers allocated.
SQLENGNSG1M	This parameter controls the number of pre-allocated 1M 64-bit buffers allocated.
SQLENGNSG2M	This parameter controls the number of pre-allocated 2M 64-bit buffers allocated.
SQLENGNSG3M	This parameter controls the number of pre-allocated 3M 64-bit buffers allocated.
SQLENGNSG4M	The parameter controls the number of pre-allocated 4M 64-bit buffers allocated.
SQLENGNSG6M	The parameter controls the number of pre-allocated 6M 64-bit buffers allocated.
SQLENGNSG16M	The parameter controls the number of pre-allocated 16M 64-bit buffers allocated.
SQLENGNSG64M	The parameter controls the number of pre-allocated 64M 64-bit buffers allocated.
SQLENGNSG128M	The parameter controls the number of pre-allocated 128M 64-bit buffers allocated.
SQLENGNSG256M	The parameter controls the number of pre-allocated 256M 64-bit buffers allocated.
SQLENGNSG512M	The parameter controls the number of pre-allocated 512M 64-bit buffers allocated

Note: Using the defaults requires a minimum of 16G

Syntax for modifying the parameters in IN00 (default value - less than 56G) are as follows:


"MODIFY PARM NAME(SQLENGNUMSEG) VALUE(24)"
"MODIFY PARM NAME(SQLENGNSGBF) VALUE(2304)"
"MODIFY PARM NAME(SQLENGNSG1M) VALUE(16)"
"MODIFY PARM NAME(SQLENGNSG2M) VALUE(512)"
"MODIFY PARM NAME(SQLENGNSG3M) VALUE(24)"
"MODIFY PARM NAME(SQLENGNSG4M) VALUE(2048)"
"MODIFY PARM NAME(SQLENGNSG6M) VALUE(24)"
"MODIFY PARM NAME(SQLENGNSG16M) VALUE(256)"
"MODIFY PARM NAME(SQLENGNSG64M) VALUE(256)"
"MODIFY PARM NAME(SQLENGNSG128M) VALUE(1024)"
"MODIFY PARM NAME(SQLENGNSG256M) VALUE(1024)"
"MODIFY PARM NAME(SQLENGNSG512M) VALUE(1024)"

The default value for each parameter is based on the MEMLIMIT for the started task.

If MEMLIMIT is greater than 32G then the default values are:


SQLENGNUMSEG    24      SQL SIZE OF MAIN BUFFERS
SQLENGNSGBF     96      SQL MAIN BUFFERS  
SQLENGNSG1M     16      1M BUFFERS  
SQLENGNSG2M     256     2M BUFFERS  
SQLENGNSG3M     8       3M BUFFERS  
SQLENGNSG4M     512     4M BUFFERS  
SQLENGNSG6M     4       6M BUFFERS  
SQLENGNSG16M    16      16M BUFFERS 
SQLENGNSG64M    8       64M BUFFERS 
SQLENGNSG128M   8       128M BUFFERS
SQLENGNSG256M   4       256M BUFFERS
SQLENGNSG512M   2       512M BUFFERS

If MEMLIMIT is greater than 16G then the default values are:


SQLENGNUMSEG    24      SQL SIZE OF MAIN BUFFERS
SQLENGNSGBF     32      SQL MAIN BUFFERS  
SQLENGNSG1M     8       1M BUFFERS  
SQLENGNSG2M     128     2M BUFFERS  
SQLENGNSG3M     8       3M BUFFERS  
SQLENGNSG4M     256     4M BUFFERS  
SQLENGNSG6M     4       6M BUFFERS  
SQLENGNSG16M    8       16M BUFFERS 
SQLENGNSG64M    4       64M BUFFERS 
SQLENGNSG128M   4       128M BUFFERS
SQLENGNSG256M   0       256M BUFFERS
SQLENGNSG512M   0           512M BUFFERS

If MEMLIMIT is greater than 56G and less than 96G then the default values are:


SQLENGNUMSEG       24      SQL SIZE OF MAIN BUFFERS
SQLENGNSGBF        512     SQL MAIN BUFFERS  
SQLENGNSG1M        16      1M BUFFERS  
SQLENGNSG2M        2048    2M BUFFERS  
SQLENGNSG3M        16      3M BUFFERS  
SQLENGNSG4M        2048    4M BUFFERS  
SQLENGNSG6M        8       6M BUFFERS  
SQLENGNSG16M       128     16M BUFFERS 
SQLENGNSG64M       32      64M BUFFERS 
SQLENGNSG128M      16      128M BUFFERS
SQLENGNSG256M      8       256M BUFFERS
SQLENGNSG512M      8       512M BUFFERS

If MEMLIMIT is greater than 96G then the default values are:


SQLENGNUMSEG        24	SQL SIZE OF MAIN BUFFERS
SQLENGNSGBF         256     SQL MAIN BUFFERS  
SQLENGNSG1M         64      1M BUFFERS
SQLENGNSG2M         3072    2M BUFFERS  
SQLENGNSG3M         32      3M BUFFERS  
SQLENGNSG4M         4096    4M BUFFERS  
SQLENGNSG6M         8       6M BUFFERS  
SQLENGNSG16M        128     16M BUFFERS 
SQLENGNSG64M        64      64M BUFFERS 
SQLENGNSG128M       32      128M BUFFERS
SQLENGNSG256M       16      256M BUFFERS
SQLENGNSG512M       8       512M BUFFERS

The SQL function BUFFERINFO() is used to monitor the usage of the buffer pools.

For more information, see BUFFERINFO.