Independent disk pool considerations for commitment definitions

QRECOVERY library considerations

When you start commitment control, the commitment definition is created in the QRECOVERY library. Each independent disk pool or independent disk pool group has its own version of a QRECOVERY library. On an independent disk pool, the name of the QRECOVERY library is QRCYxxxxx, where xxxxx is the number of the independent disk pool. For example, the name of the QRECOVERY library for independent disk pool 39 is QRCY00039. Furthermore, if the independent disk pool is part of a disk pool group, only the primary disk pool has a QRCYxxxxx library.

When you start commitment control, the commitment definition is created in the QRECOVERY library of the independent disk pool that is associated with that job, making commitment control active on the independent disk pool.

Set ASP Group considerations

Using the Set ASP Group (SETASPGRP) command while commitment control is active on an independent disk pool has the following effects:

• If you switch from an independent disk pool and resources are registered with commitment control on the disk pool, the SETASPGRP command fails with message CPDB8EC, reason code 2, The thread has an uncommitted transaction. This message is followed by message CPFB8E9.
• If you switch from an independent disk pool and no resources are registered with commitment control, the commitment definitions are moved to the independent disk pool to which you are switching.
• If you switch from the system disk pool (ASP group *NONE), commitment control is not affected. The commitment definitions stay on the system disk pool. If you subsequently place independent disk pool resources under commitment control before system disk pool resources, the commitment definition is moved to the independent disk pool.
• If you use a notify object, the notify object must reside on the same independent disk pool or independent disk pool group as the commitment definition.
• If you move the commitment definition to another independent disk pool or independent disk pool group, the notify object must also reside on that other independent disk pool or independent disk pool group. The notify object on the other independent disk pool or independent disk pool group is updated if the commitment definition ends abnormally. If the notify object is not found on the other independent disk pool or independent disk pool group, the update fails with message CPF8358.

The current name space of the job determines which independent ASP the commitment definition is created in. If the job is not associated with an independent ASP, the commitment definition is created in *SYSBAS, otherwise it is created in the independent ASP. If the job is associated with an independent ASP, you can open files under commitment control that reside in the current library name space, i.e. they may reside in the independent ASP or *SYSBAS. If the first resource that is placed under commitment control does not reside in the same ASP as the commitment definition, the commitment definition is moved to the resource's ASP. If both *SYSBAS and independent ASP resources are registered in the same commitment definition, the system implicitly uses a two-phase commit protocol to ensure the resources are committed atomically in the event of a system failure. Therefore, transactions that involve data in both *SYSBAS and an independent ASP will not perform as well as transactions that are isolated to a single ASP group.

Default journal considerations

You should be aware of the following default journal considerations:

• If you use the default journal, the journal must reside on the same independent disk pool or independent disk pool group as the commitment definition.
• If the default journal is not found on the other independent disk pool or independent disk pool group when commitment control starts, the commitment control start fails with message CPF9873.
• If you move the commitment definition to another independent disk pool or independent disk pool group, the default journal must also reside on that other independent disk pool or independent disk pool group. If the journal is not found on the other independent disk pool or independent disk pool group, the commitment definition is moved, but no default journal is used from this point on.

Initial program load (IPL) and vary off considerations

You should be aware of the following IPL and vary off considerations:

• Recovery of commitment definitions residing on an independent disk pool is performed during the vary on processing of the independent disk pool and is similar to IPL recovery.
• Commitment definitions in an independent disk pool are not recovered during the system IPL.
• When recovery is required for a commitment definition that contains resources that reside in both *SYSBAS and an independent ASP, the commitment definition will be split into two commitment definitions during the recovery, one in *SYSBAS and one in the independent ASP, as though there were a remote database connection between the two ASP groups. Resynchroniziation may be initiated by the system during the recovery to ensure the data in both ASP groups is committed or rolled back atomically.
• The vary off of an independent disk pool has the following effects on commitment definitions:
  • Jobs associated with the independent disk pool end.
  • No new commitment definitions are allowed to be created on the independent disk pool.
  • Commitment definitions residing on the independent disk pool become unusable.
  • Commitment definitions residing on the independent disk pool, but not attached to a job, release transaction scoped locks.

Remote database considerations

You should be aware of the following remote database considerations:

• You cannot use an LU 6.2 SNA connection (protected conversations or Distributed Unit of Work (DUW)) to connect to a remote database from an independent disk pool database. You can use unprotected SNA conversations to connect from an independent disk pool database to a remote database.
• When commitment control is active for a job or thread, access to data outside the independent disk pool or disk pool group to which the commitment definition belongs is only possible remotely, as if it were data that resides on another system. When you issue an SQL CONNECT statement to connect to the relational database (RDB) on the independent disk pool, the system makes the connection a remote connection.
• The system disk pool and basic disk pools do not require a remote connection for read-only access to data that resides on an independent disk pool. Likewise, an independent disk pool does not require a remote connection for read-only access to data that resides on the system disk pool or a basic disk pool.