Version 7.4.2
 —  Introduction  —

Parallel Participant Table (PPT)

The parallel participant table (PPT) located in a database's Associator tracks all active Adabas nuclei in the cluster.

The document covers the following topics:


Acquiring the PPT

Before you can run an existing Adabas database with Adabas Cluster Services, you must run ADACNV to convert it to the version of Adabas that underlies Adabas Cluster Services. ADACNV accesses the free space table (FST) to acquire 32 contiguous blocks from the Associator and reserve them for the PPT.

ADACNV acquires 32 contiguous blocks in the Associator for each existing database and ADADEF acquires 32 contiguous blocks in the Associator for each new database. The location of the 32 contiguous blocks of Associator space is written to the general control block (GCB).

PPT blocks exist for both cluster nuclei and a single noncluster nucleus, eliminating the need to run the conversion process if switching from an Adabas cluster session to an Adabas noncluster session.

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Registering Nuclei during Session Initialization

During session initialization as each Adabas cluster nucleus becomes active, it registers in the PPT based on the setting of its ADARUN NUCID parameter. The nucleus chooses the first of the 32 PPT blocks that is not yet assigned to another NUCID. If this is not the first run of this nucleus, the nucleus reuses its previously used PPT block. The relative block number of the chosen PPT block within the PPT (a number between 1 and 32) is called the 'internal nucleus ID'.

Note:
A noncluster nucleus always occupies the first block of the PPT and its NUCID is always zero.

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Registering PLOG, CLOG, and Work Datasets for Each Nucleus

Each active nucleus writes information to the Work, protection log (PLOG), and command log (CLOG) datasets that it is using for that session. The internal nucleus ID is also written to the PLOG records.

As each Work, PLOG, and CLOG dataset becomes active, it is registered in the PPT. Information about these datasets is logged in the PPT entry of its nucleus.

When the PLOG or CLOG is merged, its PPT entry is updated with the information. ADARES and the cluster nuclei synchronize their PPT updates against one another to ensure that only one modification occurs at a time.

Work dataset, protection log, and command log information remains in the PPT, even when CLOGs or PLOGs are merged or the session terminates.

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Nucleus Termination Processing

If the nucleus terminates normally, the PPT entry is retained and marked as inactive.

If a nucleus terminates abnormally, its entry in the PPT remains unchanged until the recovery process is complete.

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Using PPT Information

The information about each Adabas nucleus maintained in the PPT is used when ADARES PLCOPY is copying and merging all active protection logs in the cluster.

It is also used during nucleus initialization to ensure that the dataset information required for autorestart and PLOG merge is available:

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PPT Unavailable

In the case where the PPT becomes unavailable for some reason, the new parameter NOPPT is added to the ADARES PLCOPY function for emergency use. It specifies that the PPT is to be ignored and that the PLOG datasets of all cluster nuclei are to be taken from the JCL.

If you need to merge CLOGs while the PPT is unavailable, run a normal CLCOPY and then use the CLOG MERGE function to merge the sequential datasets.

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SBLKNUM Parameter for ADARES PLCOPY NOPPT

The parameter SBLKNUM for the ADARES PLCOPY NOPPT function can be used in an emergency case when a last set of PLOGs must be copied and merged after the parallel participant table (PPT) in the Associator has been destroyed. In this case the ADARES utility does not know the last serial block number of the sequential PLOGs produced so far. By default, it starts numbering the blocks at 1 on the next sequential PLOG dataset. If this sequential PLOG is concatenated to its predecessor in a REGENERATE function, ADARES would report an error in the PLOG block number sequence. The SBLKNUM parameter can be used to specify the correct starting block number for the sequential PLOG produced by the PLCOPY NOPPT function.

There are two ways to copy and merge the PLOGs when the PPT has been destroyed:

  1. Without using the SBLKNUM parameter:

  2. With using the SBLKNUM parameter:

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