Using global memory areas

In UTM cluster applications, the UTM storage areas GSSB and ULS are supported at the global cluster level. The associated user data is stored in the cluster page pool.

openUTM manual “Generating Applications”, CLUSTER statement You use the operands PGPOOL and PGPOOLFS to define the properties of the cluster page pool (size, warning level and number of files). You use the DEADLOCK-PREVENTION operand to control how the system behaves in the case of locked, global storage areas (additional check or control via timeout).

TACs for accessing GSSB and ULS

In UTM cluster applications, you should assign TAC classes to programs that access GSSB or ULS storage areas. By restricting the processes working for these TAC classes, you can prevent all the processes in a node application from simultaneously accessing the GSSB or ULS storage areas. UTM rejects attempts to access storage areas if this would mean that all the processes in a node application would have to wait for a lock held by another node.

If it is possible, it is advisable to place the TACs that access GSSB or ULS in the same TAC class. Any TACs that use PGWT should be gathered together in the same TAC class since it is also necessary to take account of the PGWT wait situations.

When you have assigned the TACs to TAC classes, you can restrict the number of processes by means of either the TACCLASS or TAC-PRIORITIES statement:

• TACCLASS statement:
  The number of processes that are started must be at least one greater than the maximum number of processes that are allowed to run for the TAC classes containing the TACs which access GSSB or ULS.

• TAC-PRIORITIES statement:
  The number of processes that are started must be at least one greater than the total of FREE-DIAL-TASKS and MAX ASYNTASKS.

Examples

In the example below, TASKS=10 and ASYNTASKS=2 are generated in the MAX statement. The TACs with GSSB/ULS access are to run in TAC class 2 (TAC.... TACCLASS=2). This means:

• If the process limitation is controlled via the TACCLASS statement and TAC class 2 is able to use a maximum of 5 processes then the TACCLASS statement is as follows:

  TACCLASS 2,TASKS=5,PGWT=YES

  At least 6 processes must be started.

• If the process limitation is controlled via the TAC-PRIORITIES statement and at least one process is to be kept free for jobs whose TACs do not belong to any dialog TAC class then the TAC-PRIORITIES statement is as follows:

  TAC-PRIORITIES FREE-DIAL-TASKS=1

  At least 4 processes must be started (because MAX ... ASYNTASKS=2).