Understanding of Oracle 11g Automatic Diagnostic Repository – Part 1

INTRODUCTION

In an endeavour to move towards self managed database and provide better support solutions, Oracle 11g introduces another new feature in 11g called the Automatic Diagnostic Repository or ADR. As the name implies ADR is a automatically managed file based repository of diagnostic information such as trace files, core dumps, alert log, etc... ADR is like a mini database managing traces of multiple instances and multiple prouducts (database, ASM, CRS, etc...) with metadata of these traces being maintained under a unified directory structure. ADR promises to use consistent diagnostic data structures across products. Set of tools bundled with ADR facilitate us in analyzing diagnostic data.

As an outcome of this feature:
- Critical errors captured in the diagnostic repository show up as alerts in EM. In cases where the issue is a known issue, Oracle recommends corrective actions to be implemented by DBA.
- It is intended to make it easy for DBAs to consolidate and transfer diagnostic data to Oracle support, thus facilitating faster resolution of the issue.

ARCHITECTURE

Starting with Oracle 11g R1, traditional *_DUMP_DEST parameters are ignored and the trace location is decided based on DIAGNOSTIC_DEST parameter. If this parameter is not set explicitly, it defaults to ORACLE_BASE environment variable if this is set, if this is not set, then it defaults to ORACLE_HOME/log.

DIAGNOSTIC_DEST is the ADR root directory also known as ADR base.

Each instance of each product stores diagnostic data in its own ADR home directory. For example, in a Real Application Clusters (RAC) environment with shared storage and ASM, each database instance and each ASM instance have a home directory within ADR.

Under ADR base are multiple ADR homes. ADR home is the root directory for all traces within an instance of a product. i.e. Each instance of a product has an ADR home. Directroy structure of ADR is pictorial represented as below:

Under the ADR base there will be a folder "diag". Within this folder there will be seperate folders for each product like rdbsm, asm, crs, clients, lsnrctl, netcman, etc... Each of these folders will have seperate folders for every instance of the product.

For an instance of Oracle database, the structure is as depicted. All traces that used to be within USER_DUMP_DEST and BACKGROUND_DUMP_DEST are with trace folder. There is a seperate folder for alert log. A copy of the alert log in XML format is mainted in the alert folder.

Problem and Incident are two terms used frequently in ADR. All errors like the ora-600, ora-7445 or any other error like ora-470 that crashes database instance are termed as critical error. A critical error is termed as a Problem and is given a problem id by ADR based on it's symptoms. Each occurrence of a critical error is termed as an Incident.

Incident directory contains multiple subdirectories, where each subdirectory is named for a particular incident, and where each contains dumps pertaining only to that incident.

Metadata directory contains ADR's metadata.

HM directory contains health monitor reports which are part of ADR.

ADRCI - ADR command interpreter and EM support work bench are the two interfaces to ADR.

We will discuss these tools in our next post.

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