Connect to Oracle with SQL*Plus or SQLcl, understand the container database and pluggable databases, find the right service name, create a user with only the privileges it needs, and check basic health.
Use SQL plan baselines to stop plan regressions after statistics changes, patches and upgrades. Load known-good plans from the cursor cache or AWR, fix one plan in an emergency, let the evolve task accept better plans, and manage baselines over time.
New connections and parses fail with ORA-04031 in the shared pool or large pool. Buy time safely, find what is consuming the pool (literal SQL, high version counts, a leak, large pool users), resize SGA components and fix the application pattern behind it.
CPU jumps and sessions pile up on library cache and cursor mutex waits. Find the SQL with thousands of child cursors, read the reasons in V$SQL_SHARED_CURSOR, and fix bind handling, hard parsing and hot objects.
Long reports or exports fail with ORA-01555. Read the alert log, check V$UNDOSTAT, size UNDO_RETENTION and the undo tablespace, and fix fetch-across-commit and LOB cases.
When Oracle sessions hang on enq TX row lock contention, find the root blocker with v$session, identify the locked object and row, see what the blocker is doing, then fix it at the application rather than killing sessions by habit.
RMAN supports many backup styles, and the right one depends on database size, RPO/RTO and where backups are stored. Choose between full plus incrementals and incrementally updated image copies, set a recovery window retention, use block change tracking, send copies off-site or to object storage with immutability, and test restores.
Oracle databases can move to several cloud targets with very different feature sets, licensing rules and operating models. Compare OCI database services, Oracle Database@Azure and @AWS, Amazon RDS for Oracle and self-managed VMs on the features you use (RAC, Exadata, options), licensing, latency to applications and who operates them.
Large, growing tables slow queries, backups and purges. Partition by date or another access key so queries prune and old data drops instantly, compress cold partitions, move history to cheaper tablespaces, and convert online where possible. Check licensing for Partitioning and Advanced Compression before using them.
Oracle memory is often sized once at install and never revisited. Use the SGA, buffer cache and PGA target advisors with AWR history to see the effect of more or less memory, choose between automatic shared memory and manual settings, enable HugePages on Linux, and change in small, measured steps.
Applications fail with "no listener", "listener does not currently know of service" or "SID not known". Check the listener is running and listening on the right address, and that the database has registered its services. Then fix tnsnames, LOCAL_LISTENER and firewall problems, with commands for each step.
The instance crashes or won't mount because a controlfile copy or an online redo log member is missing or corrupt. What you do depends on which file is gone and whether a good copy exists. The options run from a simple copy to RMAN autobackup restore, CLEAR LOGFILE, or incomplete recovery.
The database mounts but won't open because a datafile needs recovery, is missing or can't be locked. Find the affected file, decide between recover, restore-and-recover or taking the file offline, and use RMAN to bring the database back with no data loss where possible.
Oracle 19c is the last release that supports the non-CDB architecture, so every database moving to 23ai must become a pluggable database. Check compatibility, describe the non-CDB, plug it into a CDB with NOCOPY or COPY, run noncdb_to_pdb.sql, and fix services and backups afterwards.
Data Pump is too slow for multi-terabyte databases moving from big-endian UNIX to Linux. Cross-platform transportable tablespaces with incremental backups keep the target in step while the source stays online, so the outage is a short final incremental plus a metadata import.
Move an Oracle database to RDS for Oracle when you want a managed service but must stay on Oracle. Check what RDS doesn't allow, size and license the instance, load with Data Pump through S3, catch up with DMS CDC, then cut over.
Move an Oracle schema and its data to PostgreSQL (self-managed, Azure Flexible Server or RDS/Aurora). Estimate effort with the Ora2Pg report, convert schema and PL/SQL, load data, and handle the differences that cause most bugs. Then run a parallel validation before switching.
Use AutoUpgrade to analyse, fix up and upgrade 19c databases to 23ai, including converting non-CDBs into PDBs. Covers the config file, the analyze, fixups and deploy modes, restore points for fallback, and the checks to run after the upgrade.
The Oracle Database commands DBAs reach for every week. Covers SQL*Plus and startup/shutdown, CDB and PDB navigation, sessions, locks and waits, top SQL, tablespaces and FRA, redo and archivelogs, RMAN, Data Guard broker, users and privileges, alert log and listener.
Generate AWR and ASH reports for the right window, then read DB time, top wait events, load profile and top SQL to find the real bottleneck instead of guessing.
Confirm the fast recovery area or archive destination is full, free space safely with RMAN after backing up archive logs, and keep it from happening again.
Unlock Oracle accounts, find which host keeps locking them with failed logins, and use profiles so application accounts don't expire in production.
Run Oracle Data Guard role changes safely with DGMGRL. Covers health checks, protection modes, a planned switchover, an emergency failover, reinstating the old primary with Flashback Database, and Fast-Start Failover.
Install Oracle Database 19c or 23ai as a single instance on Oracle Linux. Covers the preinstall RPM, storage layout, silent install, creating a CDB/PDB, memory settings, archivelog mode, RMAN backups and basic security.
Get real HA out of Oracle RAC. Covers database services with preferred and available instances, SCAN listeners, client failover (FAN, TAC and Application Continuity), rolling maintenance, health checks and common failure scenarios.
Use RMAN's Data Recovery Advisor and validate commands, restore a single lost datafile online, and perform full and point-in-time recovery of a database.
Check real usage against MAXSIZE, add or resize datafiles safely, deal with TEMP and UNDO errors, and find the segments that grew.
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