SPFILE

The SPFILE is the binary file Oracle reads at startup to initialize instance parameters: db_name, control_files, memory_target, sga_target, and many others. Unlike its text-based predecessor PFILE (init.ora), the SPFILE cannot be edited manually with a text editor — changes go through SQL commands.

How it works #

At startup, Oracle looks for the SPFILE in a default location ($ORACLE_HOME/dbs/spfile<SID>.ora on Linux). If not found, it falls back to the PFILE. Parameter changes are made with ALTER SYSTEM SET, which writes directly to the binary file:

-- Persistent change (survives restart)
ALTER SYSTEM SET memory_target = 2G SCOPE = SPFILE;

-- In-memory only (lost on restart)
ALTER SYSTEM SET memory_target = 2G SCOPE = MEMORY;

-- Both in memory and in the file
ALTER SYSTEM SET memory_target = 2G SCOPE = BOTH;

The SCOPE parameter controls where the change is applied: SPFILE, MEMORY, or BOTH.

Operational context #

The SPFILE is the authoritative source for persistent instance configuration. It must be included in RMAN backups, which handles it natively. In RAC (Real Application Clusters) environments, a single shared SPFILE on ASM governs all nodes, with per-instance values settable via the SID.* prefix.

A common mistake is manually editing the binary file: the instance will fail to start. If the SPFILE becomes corrupted, restore it from an RMAN backup or recreate it from a PFILE using CREATE SPFILE FROM PFILE.