1Z0-908 flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

SGA components

The System Global Area contains the database buffer cache, shared pool, large pool, redo log buffer, and fixed SGA, sized automatically when SGA_TARGET is set.

SPFILE vs PFILE

The SPFILE is a binary server parameter file changed with ALTER SYSTEM SCOPE; the PFILE is a text file edited manually and read at startup or with STARTUP PFILE.

Database startup stages

NOMOUNT starts the instance and reads the parameter file; MOUNT reads control files; OPEN opens data files and redo logs. Recovery may stop at MOUNT.

ARCHIVELOG mode requirement

ARCHIVELOG mode must be enabled for online backups and point-in-time recovery. Switching requires the database in MOUNT state and a restart of the instance.

Datapatch purpose

After OPatch applies binaries to an Oracle Home, datapatch runs the corresponding SQL patches against each database, updating the registry views.

Release Update patching

Release Updates and Monthly Recommended Patches replace the older PSU/CPU model; they are applied with OPatch to the Oracle Home, then datapatch to each database.

Read-only Oracle Home

A read-only Oracle Home shares an unpatched base with multiple patched homes, reducing disk use and patch time. ORACLE_HOME and ORACLE_BASE must not be nested.

Locally managed tablespace

A locally managed tablespace stores its extent bitmap inside the tablespace rather than in the data dictionary, avoiding recursive space transactions and contention.

ASSM and PCTFREE

Automatic Segment Space Management uses bitmaps in segment headers for free space and requires PCTFREE for row growth but ignores PCTUSED, which applies only to manual management.

Bigfile tablespace

A bigfile tablespace contains exactly one data file and can reach about 32 petabytes with 8K blocks; it uses a 4G extent bitmap and simplifies file management.

Undo vs temp tablespace

Undo stores rollback and read-consistency data for transactions; TEMP stores sort and hash work areas and temporary segments. Both are mandatory in every database.

WITH ADMIN OPTION

Granting a system privilege or role WITH ADMIN OPTION lets the grantee grant it onward. Revoking the original grant does not cascade to dependent grantees.

WITH GRANT OPTION

Granting an object privilege WITH GRANT OPTION lets the grantee grant that privilege on the object. Revoking it cascades to privileges granted from it.

Profile password limits

Profiles control FAILED_LOGIN_ATTEMPTS, PASSWORD_LIFE_TIME, PASSWORD_REUSE_MAX, and PASSWORD_VERIFY_FUNCTION, plus resource limits such as SESSIONS_PER_USER and IDLE_TIME.

SYSDBA versus SYSOPER

SYSDBA can start up, shut down, back up, recover, and create or drop a database. SYSOPER can start up, shut down, back up, and recover but cannot create or drop.

RMAN incremental levels

Level 0 is the base backup. Level 1 differential backs up blocks changed since the last level 0 or 1; cumulative backs up blocks changed since the last level 0.

Fast Recovery Area sizing

DB_RECOVERY_FILE_DEST sets the FRA location and DB_RECOVERY_FILE_DEST_SIZE sets its limit. Space pressure causes obsolete backups and archived logs to be deleted.

OPEN RESETLOGS

Incomplete recovery ends with OPEN RESETLOGS, which creates a new database incarnation and resets the redo log sequence, invalidating prior archived logs.

Flashback Database

Flashback Database rewinds the whole database to a past point using flashback logs, requires MOUNT state, and needs DB_FLASHBACK_RETENTION_TARGET and a configured FRA.

AWR snapshot interval

AWR captures performance statistics every 60 minutes by default; DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS changes the interval and retention period.

DB time formula

DB time equals CPU time consumed by sessions plus non-idle wait time. It excludes idle wait events and measures total database workload elapsed time.

ASH sampling

Active Session History samples active sessions every second into V$ACTIVE_SESSION_HISTORY, letting you see which wait events and SQL consumed time.

SQL Plan Management

SPM stores accepted execution plans as baselines so the optimizer uses only verified plans, preventing performance regressions after statistics or parameter changes.

Oracle isolation levels

Oracle supports READ COMMITTED, SERIALIZABLE, and READ ONLY. It never permits dirty reads, and readers do not block writers or vice versa.

ORA-01555 cause

Snapshot too old occurs when undo information needed for read consistency has been overwritten, typically from long queries or frequent commits in loops.

Row lock contention wait

A session waiting for another session to commit or roll back a locked row reports the enq: TX - row lock contention wait event in V$SESSION.

Deadlock detection

Oracle detects deadlocks automatically after about three seconds, rolls back one statement with ORA-00060, and writes a deadlock trace to the alert log.

CDB and PDB structure

A container database holds CDB$ROOT, PDB$SEED, and one or more pluggable databases. Each PDB has its own data dictionary and open mode.

Common versus local users

Common users are created in CDB$ROOT with a C## prefix and can connect to any container. Local users exist in a single PDB only.

Local undo in CDB

LOCAL_UNDO_ENABLED gives each PDB its own undo tablespace, allowing PDB cloning and point-in-time recovery without affecting the CDB root.

Dynamic service registration

PMON registers the instance and its service names with the listener using LOCAL_LISTENER. The database must be at least in NOMOUNT state for registration.

EZConnect syntax

EZConnect connects without client files using host:port/service_name, for example host01:1521/orclpdb, and is enabled by the ezconnect naming method.

DBMS_SCHEDULER job

A scheduler job combines an action, a schedule or repeat interval, and a job class. DBA_SCHEDULER_JOB_RUN_DETAILS reports each run's outcome.

Data Pump REMAP_SCHEMA

Data Pump import with REMAP_SCHEMA=old:new loads objects into a different schema, and REMAP_TABLESPACE redirects storage to another tablespace.