Archived Redo Log File Conventions in Oracle RAC

For any archived redo log configuration, uniquely identify the archived redo logs with the LOG_ARCHIVE_FORMAT parameter. The format of this parameter is operating system-specific and it can include text strings, one or more variables, and a file name extension.

Table 6-1 Archived Redo Log File Name Format Parameters

Parameter	Description	Example
`%r`	Resetlogs identifier, not padded	`log_1_62_23452345`
`%R`	Resetlogs identifier, left-zero-padded	`log_1_62_0023452345`
`%s`	Log sequence number, not padded	`log_251`
`%S`	Log sequence number, left-zero-padded	`log_0000000251`
`%t`	Thread number, not padded	`log_1`
`%T`	Thread number, left-zero-padded	`log_0001`

All of the file name format parameters for the archive redo logs, in either upper or lowercase, are mandatory for Oracle RAC. These parameters enable Oracle Database to create unique names for archive logs across the incarnation. This requirement is in effect when the COMPATIBLE parameter is set to 10.0 or greater.

Use the %R or %r parameters to include the resetlogs identifier to avoid overwriting the logs from a previous incarnation. If you do not specify a log format, then the default is operating system-specific and includes %t, %s, and %r.

As an example, if the instance associated with redo thread number 1 sets LOG_ARCHIVE_FORMAT to log_%t_%s_%r.arc, then its archived redo log files are named:

log_1_1000_23435343.arc
log_1_1001_23452345.arc
log_1_1002_23452345.arc
...