# PostgreSQL 9.0 → 9.1 GUC diff

> Core configuration parameters added, removed, or changed in boot default between PostgreSQL 9.0 and 9.1.
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> [!NOTE]
> **Fact.** The measured inventory changes from 207 to 219 settings: 12 added, 10 boot-default changes, and 0 removed.

## Added parameters {#added}

| Parameter | Type | Context | Boot default | Category |
| --- | --- | --- | --- | --- |
| [`default_transaction_deferrable`](/parameters/default-transaction-deferrable/) | `bool` | `user` | `off` | Client Connection Defaults / Statement Behavior |
| [`exit_on_error`](/parameters/exit-on-error/) | `bool` | `user` | `off` | Error Handling |
| [`hot_standby_feedback`](/parameters/hot-standby-feedback/) | `bool` | `sighup` | `off` | Replication / Standby Servers |
| [`log_file_mode`](/parameters/log-file-mode/) | `integer` | `sighup` | `384` | Reporting and Logging / Where to Log |
| [`max_pred_locks_per_transaction`](/parameters/max-pred-locks-per-transaction/) | `integer` | `postmaster` | `64` | Lock Management |
| [`quote_all_identifiers`](/parameters/quote-all-identifiers/) | `bool` | `user` | `off` | Version and Platform Compatibility / Previous PostgreSQL Versions |
| [`replication_timeout`](/parameters/replication-timeout/) | `integer` | `sighup` | `60000 ms` (1 min) | Replication / Master Server |
| [`restart_after_crash`](/parameters/restart-after-crash/) | `bool` | `sighup` | `on` | Error Handling |
| [`ssl_ciphers`](/parameters/ssl-ciphers/) | `string` | `postmaster` | `ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH` | Connections and Authentication / Security and Authentication |
| [`synchronous_standby_names`](/parameters/synchronous-standby-names/) | `string` | `sighup` | `""` (empty string) | Replication / Master Server |
| [`transaction_deferrable`](/parameters/transaction-deferrable/) | `bool` | `user` | `off` | Client Connection Defaults / Statement Behavior |
| [`wal_receiver_status_interval`](/parameters/wal-receiver-status-interval/) | `integer` | `sighup` | `10 s` | Replication / Standby Servers |
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## Boot-default changes {#default-changes}

| Parameter | PG9.0 | PG9.1 | Category |
| --- | --- | --- | --- |
| [`TimeZone`](/parameters/timezone/) | `UNKNOWN` | — (not set) | Client Connection Defaults / Locale and Formatting |
| [`krb_server_keyfile`](/parameters/krb-server-keyfile/) | `""` (empty string) | `FILE:/etc/postgresql-common/krb5.keytab` | Connections and Authentication / Security and Authentication |
| [`log_timezone`](/parameters/log-timezone/) | `UNKNOWN` | — (not set) | Reporting and Logging / What to Log |
| [`server_version`](/parameters/server-version/) | `9.0.23` | `9.1.24` | Preset Options |
| [`server_version_num`](/parameters/server-version-num/) | `90023` | `90124` | Preset Options |
| [`standard_conforming_strings`](/parameters/standard-conforming-strings/) | `off` | `on` | Version and Platform Compatibility / Previous PostgreSQL Versions |
| [`timezone_abbreviations`](/parameters/timezone-abbreviations/) | `UNKNOWN` | — (not set) | Client Connection Defaults / Locale and Formatting |
| [`transaction_isolation`](/parameters/transaction-isolation/) | — (not set) | `default` | Client Connection Defaults / Statement Behavior |
| [`wal_buffers`](/parameters/wal-buffers/) | `8 8kB` (64 KiB (8 × 8kB)) | `-1 8kB` | Write-Ahead Log / Settings |
| [`wal_sender_delay`](/parameters/wal-sender-delay/) | `200 ms` | `1000 ms` (1 s) | Replication / Master Server |
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## Removed parameters {#removed}

| Parameter | Last type | Context | Last boot default | Category |
| --- | --- | --- | --- | --- |
| — | — | — | — | — |
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## Method {#method}

The three lists compare the pinned PG9.0 and PG9.1 `pg_settings` snapshots directly. A default change is a change in the `boot_val` plus `unit` pair; `setting` is excluded so an `initdb`-generated value is not mistaken for the compiled boot default.

- [Machine-readable diff data](/data/diffs.json)
- [Complete GUC JSONL](/data/guc.jsonl)