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# Oracle SQL Cheatsheet

### Check Max Memory

* Issue:

```sql
ORA-04036: PGA memory used by the instance exceeds PGA_AGGREGATE_LIMIT
```

* Check memory:

```sql
select sum(pga_max_mem)/1024/1024 "TOTAL MAX PGA (MB)"from v$process;
```

* Check PGA limit:

```sql
show parameter pga_aggregate_limit;
```

### Check FS Size

```sql
select * from dba_segments;
select * from dba_data_files;
select * from dba_free_space;

-- IN GB:
select sum(bytes/(1024*10204*1024)) from dba_segments;
select sum(bytes/(1024*10204*1024)) from dba_data_files;
select sum(bytes/(1024*10204*1024)) from dba_free_space;
```

### Check user password expiry

```sql
SELECT * FROM USER_USERS;
```

### Check number of sessions

```sql
SELECT  COUNT(*) FROM v$session
```