SEQCACH—3990 cache mode
Use the Modify 3990 Cache Mode panel or the SEQCACH command to specify the cache mode that Db2 will use in its channel program for reading data from 3990-3 or 3990-6 controllers.
Specifying SEQ allows Db2 to define an extent of tracks from which data can be promoted to cache before a read-miss occurs. This allows the storage controllers to improve the hit ratio. Performance is also improved by allowing data to be moved between DASD and cache by cylinders instead of by tracks.
Modify 3990 Cache Mode panel
Command ===> _________________________________________________________________
Command: CURRENT
Description . . . . . . . . : 3990 CACHE MODE
Type the new sequential cache value that you wish to change to. Then press Enter.
Sequential Cache Parameter
Mode specification . . . . . ______ (SEQ or BYPASS)
Command syntax and parameters
Value | Description |
|---|---|
DB2ssid | Db2 subsystem ID or the name of the Db2 data sharing group to which the command applies. |
opertuneID | OPERTUNE system profile name (if OPERTUNE is running as a started task) or the batch job name (if OPERTUNE is running as a batch job). |
SEQ | Db2 can define an extent of tracks from which data can be promoted to cache in advance before a read-miss occurs. |
BYPASS | Db2 reads directly from DASD. |
NORESET | The changes you request remain in effect until the Db2 subsystem is cycled. |
Db2 parameter values
Field | Installation panel | CLIST parameter | ZPARM macro | ZPARM parameter |
|---|---|---|---|---|
Mode specification | DSNTIPE | SEQCACH | DSN6SPRM | SEQCACH |