User ISAM pools

A user can create and manage task-local ISAM pools with the aid of macros or commands.

Such a pool will, however, only be used for file processing if a pool link name is assigned to it by means of the ADDPLNK macro or ADD-POOL-LINK command and the POOLLNK or POOL-LINK operand is used to set up a connection between the ISAM pool and the file.

Pool link name – the link between file and ISAM pool

The ADDPLNK macro and the ADD-POOL-LINK command serve to assign an ISAM pool a pool link name in a job and to enter the name in the job's pool table. This pool link name then has to be entered in the TFT for each file that is to be processed in this pool (using the POOLLNK or POOL-LINK operand). In addition, NK-ISAM processing must be set by means of BLKCTRL=DATA or BLOCK-CONTROL-INFO=WITHIN-DATA-BLOCK.

When a file is opened, DMS checks whether a pool link name has been entered in the FCB or TFT, and (via the pool table) whether an ISAM pool exists to which the pool link name refers. If both checks are positive and if the pool and file attributes are compatible, the file is processed via this ISAM pool.

Comments on cross-task user ISAM pools

User ISAM pools are always task-local.

Commands and macros for cross-task user ISAM pools are still accepted for reasons of compatibility, but no longer result in such a pool being generated. Instead, DMS uses a standard ISAM pool in which the size specified beforehand by the user is not fallen below and the assignment of files to pools is retained.

The following diagram shows the actions which must be initiated by a job working with a user ISAM pool at the program interface.

Figure 35: Actions for file processing with ISAM pools (macros)

The following table shows the macros available to the user.

Macro	Function	Action see figure 35
CREPOOL	Create an ISAM pool. for a cross-task pool, the system checks if the pool already exists.	1 -> 2
ADDPLNK	Define the pool link name: this name is placed in the pool table.	2 -> 3
FILE/FCB LINK=name POOLLNK=name BLKCTRL=DATA	At OPEN time: set up the link between the ISAM pool and the file.	3 -> 4 (OPEN) 4 -> 3 (CLOSE)
REMPLNK	Delete the pool link name entry from the pool table.	3-> 2
DELPOOL	“Delete” the ISAM pool: release space in class 5 memory or clear the link to the cross-task pool if other jobs are still using the pool.	2 -> 1

Table 53: Overview of the ISAM pool macros

The following diagram shows the actions which must be initiated by a job working with a user ISAM pool at the command interface:

Figure 36: Actions for file processing with ISAM pools (commands)

The following table shows the commands available to the user.

Command	Function	Action see figure 36
CREATE-ISAM-POOL	Create an ISAM pool. for a cross-task pool, the system checks if the pool already exists.	1 -> 2
ADD-ISAM-POOL-LINK	Define the pool link name: this name is placed in the pool table.	2 -> 3
ADD-FILE-LINK LINK-NAME=name POOL-LINK=name BLOCK-CONTR-INFO= *WITHIN-DATA-BLOCK	At OPEN time: set up the link between the ISAM pool and the file.	3 -> 4 (OPEN) 4 -> 3 (CLOSE)
REMOVE-ISAM-POOL-LINK	Delete the pool link name entry from the pool table.	3-> 2
DELETE-ISAM-POOL	“Delete” the ISAM pool: release space in class 5 memory or clear the link to the cross-task pool if other jobs are still using the pool.	2 -> 1

Table 54: Overview of the ISAM pool commands