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IDMS SYSTRACE table size and startup messages DC390020 DC390007

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Article ID: 257704

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Updated On:

Products

IDMS IDMS - Database

Issue/Introduction

How much space is allocated for the IDMS SYSTRACE system trace table? 

We turned on SYSTRACE in the IDMS SYSGEN. Tried different settings for the TRACE TABLE SIZE  but the amount of storage used by CV according to the startup messages is always exactly the same: 

DC390005 Vn RHDCPARM FREESTG RELEASED .... 2,000K
DC390006 Vn REGION NEEDED TO START UP ....     9,232K
DC390020 Vn TOTAL AMOUNT OF XA STORAGE...  34,304K
DC390007 Vn SYSTEM CONFIGURATION SIZE ....   41,536K
DC390008 Vn STORAGE RETURNED TO OPSYS..        656K

Is there a recommended value for the size of the system trace table? 

Can the system trace table and adjunct table be dynamically allocated and the sizes changed?

Environment

Release : 19.0

Resolution

The startup message DC390006 REGION NEEDED TO START UP is only for below the line storage, the system trace table is allocated in 31 bit storage.

The DC390020 TOTAL AMOUNT OF XA STORAGE message does not include everything, article 112407  explains this.

Like scratch and buffers, the system trace table is allocated later in the startup process so is not included in any of the storage startup messages.

In z/OS we allocate a copy of the system trace table for internal processing, so the size used is double the size specified for the table size.
The system trace table is not in the storage pools, IDMS does a GETMAIN for 31-bit operating system storage for the table.

Unless you have a specific problem that needs to be traced just allocate the default system trace size of 4MB. 

If you're trying to catch a storage overlay then you should make the system trace table a size of 20M because storage overlays could happen long before the actual abend.

The adjunct trace table can be dynamically allocated or it's size changed with command:

 DCMT VARY TRACE ADJUNCT SIZE 5M

You can also dynamically change the size of the system trace table with command:

DCMT VARY TRACE TABLE SIZE 20 MB

To make the changes permanent the changes have to be made in the SYSGEN:

MODIFY SYSTEM nnn
TRACE SAVE OFF TABLE SIZE IS 20 MB
ADJUNCT SIZE IS 5 MB.

To check the current size settings use command:

DCMT D TRACE

System tracing (SYSTRACE):     ON
            Trace table size:    20 MB          Address: 39A40000
        Adjunct table size:    10 MB          Address: 36603000
Save: OFF          Driver: INACTIVE             Area: DDLDCLOG

Additional Information

See IDMS documentation sections SYSTEM Statement Parameters Information, DCMT VARY TRACE, DCMT DISPLAY TRACE and Enhanced System Tracing.